Choose Acrylic for Most Jobs
Acrylic caulk is easy to use, easy to smooth out and easy to clean up. And since it offers reasonably good flexibility and adhesion, it's a good choice for most exterior gaps narrower than 1/4 in. Some acrylics are labeled 'acrylic latex.' With others, you have to read the fine print to find 'acrylic.' Price is a good guide to quality; bypass the cheap stuff and spend a little more per tube. Saving a few bucks on the seals that protect your home from water damage is a bad bargain.