Straight herpetology is more of a research-based job, if you want to do field-study and such, then it's a good choice...but you won't get as much hands on husbandry/health-type experience with herpetology as you would working as a vet that specializes in reptiles...also, if I am correct...herpetology is similar to zoology as far as non-research job openings are concerned...which means there aren't many jobs available at zoos and the like...unless you start your own!
Personally, I'm starting my 3rd year as a biology major, and I'm concentrating in organismal bio and ecology...to narrow down to something like herpetology you usually gotta go to grad school...
Good luck with your choice! I think whichever way you decide to go, you'll find it to be a rewarding experience.