If you go auto, spend the BUCKS and get a good auto. The cheapo versions are not "hydrostatic". When they get wet from rain or humidity, you're replacing the mechanism.
I have the cheapo model, and disabled the auto fire components because I got tired of replacing the mechanism.
ALSO, they don't qualify as a pfd unless you're wearing them. I would have gotten a ticket a couple weekends ago, if I could not produce other PFD's because we were not wearing the inflatables........Fortunately, I keep 2 adult sized PFD's under the seats.
Later,
Geo