In bodies of water with strong populations of smaller fish, I usually opt for smaller blades that mimic the appropriate-sized forage. Under post-cold front conditions when fish can be lethargic, I'll step down to a smaller blade, if I use a spinner at all under those conditions. I usually only use spinners and spinnerbaits when the fish are more aggressive. Spinner-type baits seem to work best in bodies of water with good populations of fish or with very aggressive fish. Bass and pike are two examples of fish that can, under the right conditions, be very aggressive feeders and thus are very susceptible to flashy bladed baits.
Speed is another consideration.
As a rule, the more active the fish, the faster the presentation. Typically fish will become increasingly active as the water warms. Colorado spinners and moving at more than 2 miles an hour, and have caught bass until my arms ached working big-bladed spinnerbaits and fast as I could retrieve them. Bigger blades also have a tendency to ride higher in the water. One of the tricks in a lot of bass fishermen's bag is to change out the standard spinnerbait blade for an oversized No. 6 or No. 7 and chug that bait at or just under the surface like a buzzbait.