SOSpenders, Mustang or ???
I use a manual. They don''t go off in your trunk if you carry them about a lot. Automatic means you can be knocked out and it will pull the cord for you. Both advantages are good.
I would suggest you go with one that has the harness built in. You do want the harness to fit well or you can get hurt in a fall.
Having a second harness tangle up in your inflatable vest could be a bad deal from both directions. when built together it won''t happen.
Both brands make versions for various parts of the military. They both are tough. I also have a Mustang float coat that is nice when it''s cold out. They cost about the same as a vest.
In the end the one that fits well and you wear all the time is the best.