I think its easier to play a season as an AL team. Since pinch hitting doesn't occur nearly as often you have the luxory of having 2 guys off the bench that are there mainly for their defensive skill. Sure you've got to pay the DH, but your bench doesn't have to be all that strong, just need a guy that can cover you defensively at SS, 2b & CF, and a guy w/ a better stick that can cover you at the corner spots to give guys rest. Rotate those 2 guys around at different positions thru the coarse of a season and your starters should remain rested.
In the NL you're going to be using a pinch hitter 1-3 times in a 9 inning game. You'll still need a backup SS type (which on my teams usually has a weak stick), but you've got to have competant guys that can pick up a key pinch hit or two. So you're saving money on the DH, but you may need more money invested into your bench. I've also found that there isn't much room for an all hit, no field kind of guy. No where to hide him other than as a pure pinch hitter. I definently use my bench on my NL teams more than my AL teams (injuries aside). I find myself hoarding more specialists w/ my AL squad for the bench, while my NL teams I like guys that are more versatile.