Which league has the All-Star edge?

As the American League and National League face off in the All-Star Game presented by Mastercard tonight (7:30 ET on FOX), it's only natural to wonder which side has the advantage. Of course, by definition, every player in this game is a star; even the weakest player in the game, whomever you think that might be, is still a fantastically great baseball player. Both rosters are stacked, obviously. It's worth noting, however, that the AL is 93-82 against the NL in Interleague Play this year, continuing an annual edge they've had every year since 2003, and they've won 16 of the past 20 All-Star Games -- including a current run of four in a row.
So which side has the edge? We'll check in on each position, though know that this, like all things All-Star, is for fun. There are dozens of superstars here.
(For ease of comparison, we'll use Weighted Runs Created Plus, or wRC+, a park-adjusted hitting stat that sets "100" as league-average. A 120 wRC+, for example, can be read as "20 points above league average.")
Catcher

Already, we find ourselves with a question. Do you prefer the best individual player? Or the greatest depth? If this were a normal game, with the starter expected to play every inning, then we're going with the best catcher here, San Francisco's Buster Posey (.324/.406/.498, 142 wRC+), who is having one of the best seasons of an elite career, and has done so while taking the most plate appearances of any catcher.
On the other hand, Yadier Molina, who turns 35 on Thursday, is not having one of his better seasons (.270/.303/.411, 82 wRC+), while Salvador Perez (.290/.318/.532, 118 wRC+ ) and Gary Sánchez (.276/.360/.491, 127 wRC+) are mashing. It's very fair to say that Molina's skills at handling a staff don't get quantified well in most stats; it's also fair to say they may not apply as much catching the last few innings of an exhibition with unfamiliar pitchers. We'll take the AL's depth.
Small advantage: AL
First base

In Justin Smoak (.294/.360/.575, 144 wRC+) and Yonder Alonso (.275/.372/.562, 148 wRC+), the AL has two of baseball's most exciting stories, a pair of regularly underpowered first basemen who made significant changes to their game and had it pay off so well that they actually managed to keep Miguel Cabrera and Eric Hosmer out of the All-Star Game.
Even so, the NL is just absurdly stacked at first, to the point that Eric Thames and Anthony Rizzo aren't here, and it'd be even deeper if we were considering Cody Bellinger a first baseman rather than as an outfielder. Paul Goldschmidt (.312/.428/.577, 153 wRC+) may be the leading contender for the NL MVP Award right now; Joey Votto (.315/.427/.631, 167 wRC+) is leading the NL in slugging in addition to his usual elite on-base skills; and Ryan Zimmerman (.330/.373/.596, 148 wRC+) is having a comeback story just as good or better than Smoak or Alonso.
Big advantage: NL
Second base

Jose Altuve (.347/.417/.551, 161 wRC+) keeps proving year in and out that he's not just "a good hitter for a little guy," he's just a good hitter. At the break, he's tied for the fourth-best hitting line in baseball, which is impressive enough without even considering his plus speed (18 steals) or solid defense. NL starter Daniel Murphy (.342/.393/.572, 146 wRC+) is showing again that his 2015 postseason breakout was no fluke, but given Altuve's edges in hitting, fielding, and running, it's easy to lean toward the AL here.
The backups don't change the equation, either. Colorado's DJ LeMahieu (.307/.364/.389, 85 wRC+ is hitting a lot more like the decent batter he was in 2015 than the star he looked like in 2016, though his fielding is still solid; Pittsburgh's Josh Harrison (.280/.361/.436, 114 wRC+) has done the opposite, rebounding from a poor 2016. Still, the AL gets to follow Altuve with Robinson Canó (.275/.332/.481, 114 wRC+) and the very underrated Jonathan Schoop (.295/.347/.536, 129 wRC+).
Advantage: AL
Shortstop

Here we have an interesting combination of three bright young stars and the unexpected breakout season of Cincinnati's Zack Cozart (.316/.394/.547, 143 wRC+). He's followed by Corey Seager of the Dodgers (.298/.395/.502, 139 wRC+), who is having basically the same season as the 2016 version (.308/.365/.512, 137 wRC+) that earned him a third-place MVP finish.
So that's a pretty formidable duo, depending on where you land on Cozart's season looking nothing like the five that came before it. Still, the AL has Carlos Correa (.325/.402/.577, 161 wRC+), not only having the breakout year we thought might come last year, but also being one of the hitters tied with Altuve in the top 5. This would be an easy advantage if not for the confusing step back of Francisco Lindor (.252/.312/.456, 98 wRC+) on both sides of the ball, but the greatness of Correa slightly carries the day.
Very small advantage: AL
Third base

Remember when we said that first base in the NL was overloaded? That's nothing compared to third base, where Kris Bryant, Anthony Rendon and Travis Shaw didn't make the team, and Justin Turner (.377/.473/.583, 183 wRC+) required the Esurance All-Star Final Vote to get on for the first time. Nolan Arenado's raw line (.301/.351/.554, 113 wRC+) gets a bit of a boost from his home park, but he's actually hit one more homer on the road, and his elite defense plays anywhere. And then you still have Jake Lamb (.279/.376/.546, 129 wRC+), who has improved each year in his career.
It's not like the AL is barren here, of course. Starter José Ramírez (.332/.388/.601, 157 wRC+) has turned himself into baseball's quietest superstar, and Miguel Sanó (.276/.368/.538, 136 wRC+) has as much raw power as anyone in the game -- yes, even you-know-who in New York. Throw in the most powerful season of Mike Moustakas' career (.270/.304/.559, 120 wRC+), and you get why we've been calling this "the Golden Age of third base" for a while now.
Advantage: NL
On to an outfield lightning round, where we're making our best guesses as to where each fielder will play; some will inevitably end up in a spot other than their primary position.
Left field

George Springer (.310/.380/.613, 164 wRC+) has been the third-best hitter in baseball, and he's easily the best player in this group, while Justin Upton (.265/.350/.491, 122 wRC+) never quite seems to get the notice his numbers deserve. Then again, doesn't that apply to Marcell Ozuna (.316/.374/.566, 144 wRC+), too? Do you believe more in Michael Conforto's very good season line (.284/.403/.542, 148 wRC+), or that he's hit just .209/.376/.313 (98 wRC+) since June 1? We'll take the certainty of Springer.
Very small advantage: AL
Center field

Mookie Betts (.272/.351/.490, 116 wRC+) isn't hitting like he did last year, but the value he adds on defense and the bases still makes him one of the game's most valuable players, though when he leaves, we may see Michael Brantley (.304/.367/.440, 114 wRC+) playing somewhat out of position here. Is that duo better than the all-around game of Charlie Blackmon (.319/.372/.583, 128 wRC+) and Ender Inciarte (.302/.350/.407, 99 wRC+, with elite defense)? Not by a lot. But yes.
Small advantage: AL
Right field

What do you even do here? Bryce Harper (.325/.431/.590, 161 wRC+) and Aaron Judge (.329/.448/.691, 197 wRC+) are probably two of the three biggest slugging superstars in the game. We'd be remiss to not note how good Avisaíl García (.310/.353/.497, 124 wRC+) has been here as well, and the NL may get to counter with Dodgers sensation Bellinger (.261/.342/.619, 161 wRC+) here, given the logjam at first. There's no wrong answer here. But as long as Judge is on a historic pace -- and he is -- he alone earns our edge.
Small advantage: AL
Designated hitter

We don't know yet who will back up hometown hero Giancarlo Stanton (.277/.360/.572, 139 wRC+) as the NL's designated hitter, while the AL will roll with Corey Dickerson (.312/.355/.548, 139 wRC+) and Nelson Cruz (.292/.372/.520, 139 wRC+). You'll notice the three all have an identical "139 wRC+" at the end of their lines, and defense doesn't matter at DH. If that's not enough for a tie, we're not sure what is.
Advantage: Push
Starting pitchers

As you'd expect, there's just a ton of talent on both sides here, but while the NL loses only Clayton Kershaw due to starting on Sunday, the AL loses Yu Darvish, Corey Kluber and Michael Fulmer, plus Dallas Keuchel is injured. It's too hard to just look at "best pitcher" here -- go ahead, try to choose between Chris Sale or Max Scherzer -- but as a group, the NL starters have a 2.78 ERA and a 30.2 percent whiff rate, while the remaining AL starters have a 3.16 and 26.4. Good enough for us.
Advantage: NL
Relief pitchers

Similar to Sale vs. Scherzer, just try to pick between Craig Kimbrel and Kenley Jansen. It's not easy. Trying to choose between these groups is just splitting hairs, so let's do exactly that. The AL group has a 36.6 whiff rate, compared to a nearly identical 35.8 for the NL. The NL has a lower ERA of 1.64 compared to 2.12, though ERA isn't a great metric for relievers. A more advanced quality of contact metric shows an essential dead heat. Despite Andrew Miller, we'll give the NL the tiniest of edges because Jansen can be supported by Wade Davis and Greg Holland, while Dellin Betances' ongoing control issues are slightly concerning. 
Extremely small advantage: NL