I just got a Richardson after years of vest wearing.
Richardson: 3 tray model.
Pros: Lots of flies, they're easier to see, easier to get to, easier to organize, and you basically have a table right there. Holds my floatant readily available. And a pouch on the front holds my tippet where its easier to get to. Cooler than a vest, more ventilation. Much easier on my back. Maybe its because I don't take as much unneeded crap, but its lighter. Don't have a problem with visibility, though I am fat.
Cons: Line does hang on it. Had to put a pouch on the strap for keys, shot, flashlight, etc. Leader straigtener, nips, thermometer, and forceps hang off the straps and swing around when I walk. On rare occasions if I'm carrying a lunch along I'll still have to wear a vest, in addition to the chest box.
Vest:
Pros: You can carry more stuff.
Cons: You end up carrying more stuff. Its harder to get to and easier to lose (I always left pockets open and leaned over). I can't keep it organized either.