Hit-Air. My daughter and I both wear them every time we ride and don't notice they're on. Tried other makes before we bought but were not as comfortable.
I second Hit Air. Very good and have more coverage than Point 2. They are as JJSBH says a lot lighter and also inflate outwards rather than the Point2 that inflate inwards.
Both Point 2 and Helite now do airjackets which only inflate outward and are specifically designed for hunting. You can also get a full hunt coat with an airjacket concealed inside it - again both point 2 and helite make them.
My personal preference is for the helite. The canisters are easier to replace on the move. Fiddling about with an allen key whilst trying to remount is not my idea of fun. Also for me the Hit Air comes up too long -I'm relatively short in the body - and would actually cause a neck injury rather than prevent it. My new hunt airjacket is a Helite hunter in navy to match my jacket. You can turn the collar section out so your hunt collar (if you have one) is still clear. The colour is a good match and you have to look twice to see I'm wearing it.