I assume you are talking very tight turns. I like down-shifting before I get into the turn. Because I want to concentrate on the road surface, if anyone is in my lane, if I can really gun it, or if I have to brake hard. On tight uphill or downhill curves around here, you have to countersteer before the turn, turn the handlebar while in the slowest part, and not fall over or cross the double yellow. You don't want to be in the wrong gear. Plus, I like the feel and sound of putting the engine, transmission, wheels and curve in harmony.