I have never understood the debate over this. Here in the UK they are considered a completely normal piece of baby safety equipment. You wouldn't put your child in the car without a car seat, you don't let him walk alongside a busy road without a harness.
I do understand that in the US, you are less likely to be walking along a busy street, but even so, if you are concerned enough about the safety of your dog to keep him on a leash, then I think your baby deserves the same consideration. it only takes a second for a child to let go of your hand and run straight into the street and be hit by a car.
we prefer the chest harness style - there is no way that is going to slip loose. We also use them in high chairs, and strollers, so it's quite commonplace to see kids wearing them.
When my daughter was a little older, we moved onto a wrist strap and she absolutely hated that - it's not pleasant to have someone tugging on your wrist, it really interfers with your movement. So, instead of attaching it to her wrist, we attach it to the back of her trousers, usually through a belt loop, I've also put it through a waist pack. The harnesses I have used could not slip off it they were attached through a belt loop, it's a sealed loop at one end, you put that through the belt loop and then pull the tail of the harness through the sealed loop, it is completely secure and there is no velcro involved.
tricia - my dd went through a stage of not wanting to wear it when she was around 2 - although with her it was not wanting to put it on. We found if we put it on in the house then she accepted it, but if we waited until she wanted to walk and then tried to put it on, she would object, quite strongly at times.
Since traffic is a big issue over here, I just had a no harness no walking policy, much like the no carseat no trip policy I am sure you all have, and she learned pretty quickly that she had to wear the harness.
Bev