As somebody who had lots of experience defrosting freezers back in the days before frost free units became available, I strongly suggest going with the frost free model! Defrosting is a major pain and takes a lot time to do well. In addition, you have to do something with all the stuff you take out of the freezer while you're defrosting so it doesn't begin to thaw. Believe me, $50-75 is a small price to pay for the convenience.

I prefer the upright models simply because of convenience and because they take up less floor space. The chest types probably are more efficient since the cold air just "spills out" when you open an upright model. However, we don't open the freezer very often, so that isn't much of a factor IMHO.