The manual defrost freezer is deffinately better than auto due to the exact reasons you stated. I sell appliances for a living and would never push a frost free for that reason. As far as storing venison, I keep it for a year plus sometimes and it is fine. I make sure it is double wrapped nice and tight and I never have a problem with freezer burn. The only recommendation I have for you on putting a freezer in the garage is to have some sort of heat in the garage or some heat tape on the bottom of the compressor to keep it warm in the winter so the oils don't get coagulated and burn out the compressor from hard starts. If you live in a warm climate 50 degrees and above, I wouldn't worry about it.