It is definitely harder catching largemouth in the winter when the waters are near freezing. They suspend in the warmest part of the water column and they will not move far to eat, so you have to drop it right on their nose most of the time. I have bounced a finesse worm right between their eyeballs and they didn't even budge before. Not even to spook.
Smallmouth are a little more active, since they prefer a cooler water. I have caught them in the rivers during the winter.