Quite a nice problem you have there, having two good keepers in league two is rare to say the least
I would have to say put them both on rotation and let them have 5 or so games per stint, then after they have had about 10 games each you should be able to get a feeling for who you like more, remember average rating is not everything. check his form on his form tab, this gives you some good info.
When you've found the one you think are #1 it dosn't really matter
IMO if you kick him up to important or keep him as a rotation, either way keep the other guy on rotation, a bad stretch of form, injury or even a game where you feel he will contribute more is a good oppertunity to give him a go and raise his value
Good Luck