M.C.
you still would probably save if you bought cloth diapers. For that old of kids I would buy some gender neutral one-size cloth diapers... maybe 12 -16 and use them on both kids. Chances are your youngest will still be in diapers for a while now. If you take good care of the diapers you could possible even resale them or donate them to a place like "the cloth diaper foundation".
I use "happy heinies" one size pocket diapers, and WAHM one size pocket diapers from "cheeky diapers" they run about $17-$20/diaper- either one. get a cheap step-can and use super basic laundry detergent- no fabric softeners, ideally fragrance free. wash on hot- and do an extra rinse
Shop around if you go with a "big brand" like fuzzibunz, bumgenious, or happy heinies. Some smaller WAHM businesses make just as good of diapers for less though! Whatever you do, keep in mind that it is usually cheaper to buy diapers in a package deal than it is to buy them one at a time. For how many diapers you'll need I cannot imagine the cost being more than $320... probably less! If you went with 12 one-size diapers at the "low end" you could only spend about $210. Do you think you'll use another 10 cases of diapers before your done potty training? It is up to you!
Good Luck either way!
-M.