These sticks are a great balance between responsiveness and durability. They're about the thickness of a 5A, but longer, so you can really get a heavy stroke out of them. They will stand up to hard hitting, but aren't too thick for delicate techniques (as a 5B-size stick might be).
Unless you need the nylon tips for very specific cymbal techniques, go for the wood tip. In my experience, nylon tips can sometimes pop off from the end of the stick, and the sharp corner underneath will damage your drum heads (though this is something i've noticed with Vic Firth sticks far more than with Pro Mark).
I'm playing in some very hard-hitting bands, and these sticks never break. They will wear down, as any stick does, but you can rely on them to do the job.