There are so many pro and cons about collars and harnesses; who's to know what to do?

I've often thought about the harness vest, but I'm so afraid the velcro won't hold!

Can I please get comments and opinios from those who use them. Right now I use harnesses for my babies, but they are always chewing them (espcially in the car), but when they are in their fences yard, I don't have anything on them, which I worry about; the little buggers are like little Hudinis, they can escape from almost anything.

Opinions please.