Board Thread:Game Discussion/@comment-5573466-20130505204212/@comment-8284783-20130507224541

So far, the only surefire way of determining whether I'll be getting lots of exp or not from upgrading is the actual upgrade cost.

The more a card adds to your upgrade costs when you select it, the more exp it will give.

It is directly related to how much it will sell for, as well as its overall power level.

That is why you will see some R1s having as much of an effect (if not more) than certain R2s, and I'm sure the same could be observed about certain R2s and R3s (although it wouldn't be as close, since there are no R2s that are as powerful as even the crappiest R3). You could still try upgrading by using a bunch of Razorclaws, then do the same using a bunch of Cyclonius/Chromia and I'm sure there wouldn't be that much of a difference (as opposed to upgrading using, say, a bunch of Reflectors vs Optimus Prime).