To me it breaks down as such:
Rotation - Nats hands down even without Stras. I'd take Gio, JZimm, EJax and Det over everybody in the Braves rotation.
Bullpen - As a whole, the Nats I think put up more zeroes over time but the Braves have a much more consistent and dominant closer in Kimbrel.
1B - LaRoche has better D and a similar bat to Freddy. Advantage ALR.
2B - Uggla hits bombs but little else and his defense is horrendous. Danny is a K machine but his defense is GG caliber if Brandon Phillips didn't exist. Slight advantage to the Nats I think.
3B - Zimmerman has a defensive edge over Chipper. Chipper is an amazing hitter even at his age. This one is a push.
SS - Desmond is having a career year both defensively and at bat. Simmons is no slouch though. Desmond by a bit.
C - McCann over whoever catches for us by a big margin. Not even close.
RF - Jason Heyward over Werth. Werth has too small a sample size to declare him a better hitter and Heyward has impeccable D unless he is watching Harper hit. Braves.
CF - Bourn over Harper. Harper is slumping just as he should be at 19. It's easy to see that harper has a much better future than Bourn but Bourn has amazing D and makes up for his K's with a high average and some pop.
LF - Prado is slumping but can play LF very well. Doesn't have the best arm since he does have an IF arm. Morse has an IF arm as well and posts a .300 average which is close to what Prado is doing. Morse edges him out on power and overall I think this is a push.
Benches are close. Utility MI between Janish (or Jack Wilson) and Lombo has the advantage to Lombo because he isn't hitting under .230 and can field quite well as can the other guys. Reed Johnson has an edge over Moore just because he has lots of experience coming off the bench and Moore is basically a starter playing on the bench as a rookie. Bernadina provides decent hitting and good defense in the field and makes him a slightly better choice than Diaz. Hinske and Chad Tracy are a push. Both provide identically the same thing. Backup C, well Ross is way better than Flores.
Nationals have - Rotation, overall Bullpen, 1B, 2B, SS, LF, and 2 out of 4 bench positions giving one bench position a push.
Braves have - 3B, C, RF, CF and 2 out of 4 bench positions.
That has the Nats with a slight advantage of 8 to 6 overall, but again the margins are slim here. Aside from Catcher as someone else has stated, there aren't many spots that Nats are greatly worse than the Braves. Same goes for the braves even though I feel that the Nats have by far the better rotation.
This comes down to the wire folks. Going to be a tough stretch run for both teams and I honestly wouldn't be suprised if both make the playoffs and get knocked out to a hot team that is better rested.