here is my opinion.
due to the low lp of each guy, they are naturally going to take a lot of 3s, even at a 0. with their high FT shooting, you are definitely giving something up by forcing the 3 instead of driving. even great 3 point shooting is not as efficient as good ft shooting. at a fantastic 3 pt % - say 42% - you are at 1.26pts per shot. with free throws, at a less than stellar 75%, you are at a much better 1.5pts per shot. plus, you drew a foul (which has significant benefit).
generally, fast athletic guards can draw free throw attempts like a good big man. but only by driving. 3 pointers result in far fewer ft attempts - although, more than they should, at least compared to the real world. so, you can't just compare fg% to 3pt%. when you take out 3pta out of fga and come up with 2pt%, you can't just multiply 3pt% by 1.5 and decide which is more effective. i used to do this, early in my career, but its way off. how exactly do you compare? i am not sure. but i know you take a LOT more fts based on 2pta than 3pta. and, its damn near impossible to value the additional fouls you draw.
let me just give an example, and YOU can judge how realistic it is (i think its reasonable, but probably not exact). say a 2 point shooting guard, shooting 75% fts, takes 1-2 more fts per game. they can easily take 1 more, IMO, and i think 2 is not unreasonable. that is .75-1.5 extra points per game off free throws. say the 3 point shooting guard takes three to six more threes per game than the other guard. thats quite a bit, but, so is the additional fts. then, at 50%/40% for 2s/3s (that part is definitely fairly realistic), the 3s merit .2 more points per shot (40% * 3 = 1.2, 50% * 2 = 1), which gives .6-1.2 more points per ft.
now, you may say the above overstates the additional fts. i have no end of season teams to pull stats off of, but i think it is at least in the ballpark. in that case, the 2 point shooting guard did better. and the additional foul he drew is pretty valuable, too, although i have no idea how to value it really.
one more point to add. based on the shooting nature of your team, in terms of 3s vs 2s, you certainly affect your opponent's defensive settings, at least in the post season. a heavy 3 point shooting team and a light 3 point shooting team both suffer as a result of this. therefore, i can EASILY see the argument tipping in fairly unbalanced cases. in the above case, on +2, you are probably looking at between 1.5 and 2x more 3pta per game than your opponents. all those + defenses are going to hurt you, a lot. i would bet going to +1 or 0 would help this. similarly, if you have a guard like the above on a team with no 3 point shooters, i can see a lot of - defenses coming, and that could definitely tip the scales in favor of a +1 or +2.