I always used "bottom" in order to describe a dog's ability to accept pressure and respond appropriately (i.e. not fold up, sulk, pout, or get so stressed he/she cycles through every choice but the correct one). To me, it's different than "drive." Maybe I'm using the term incorrectly, but if too much bottom is a bad thing, I'll take more of that. I'd rather have "too much" bottom than not enough.