My bike brought a set of "FSA's Powerdrive" crankset which I can't find any good information online for. I've been thinking getting some Sugino's 165mm what I have now are 175mm. My question is, would I really notice the difference in performance/smoothness? I was thinking of just changing the cranks, but why now go the whole way and do with the BB too...

the FSA bottom bracket won't fit the Sugino cranks. FSA is a spline fitting and Sugino is a square taper. You have to do a complete change. As for the feel of the cranks, like everything else, it's a personal thing. You will decide after having used each one which you like best.