I have heard of some Rossi lever actions having trouble feeding the shorter .38 and .44 special rounds but your gun should be able to feed any of the regular .44 magnum rounds.
As far as which might work best, that often varies from rifle to rifle and the only way to determine your guns preference is just to try.
As far as ammo pricing and availability, its still a crap shoot for everyone. The priced you quoted do seem high, but I have not tried to buy .44 mag ammo recently. My only advice would be to search the big online ammo retailers and see if you can do better.