I can't comment on the vest for a water dog, but for an upland dog I would never use a vest. I got a blaze vest for my English Setter and only used it on him a few times. It's hard to get a good fit and he ended up getting chafed pretty good on the inside of his front legs.
Even worse than the chafing is the concern that the dog will catch the vest jumping over a snag on a log and seriously injure or impale himself. When I watch my dog run, I think he is really efficient with his jumping and dodging to avoid injury, but adding a separate piece of equipment may throw his timing and judgement off. Once I thought about it, I decided to not have him wear the vest. He is a Llewellin colored setter and easy to see in the brush, so I don't need the vest for visibility.