You live in Oklahoma and you need reasons other than, "more stable in the wind?"

Greater stability and visibility are usually major selling points. The landing gear on .60-sized trainers is often more robust than on .40-sized counterparts. I don't have enough specific hands-on time with Alpha .40s and .60s though, to make that assessment.

I will just say that the only disadvantage to a .60-sized Alpha compared to a .40-sized Alpha is cost. The plane will cost more to purchase, and it will use fuel at a modestly higher rate. If cost factors into your decision, then the Thunder Tiger Easy Trainer 40 super combos are your best value.