The simple answer is that polyurethane caulking is the best. Oil-based caulking sticks well but tends to crack over time. Pure latex caulking is almost useless. Latex acrylic and thermal plastic caulking are very good, but they too will crack over time, because they have a tendency to shrink and become brittle. Unlike the others, silicone caulking does not crack or shrink and remains very elastic over a prolonged period. Unfortunately, it tends to lose its grip on brick. Polyurethane caulking is the best overall caulking for all outdoor uses. Over 90 percent of it is composed of solids, so it remains very elastic and will not crack. You can also paint over it. It may be a little bit more expensive, but it is a good investment. It will remain in place and do its intended job years longer than the other types.