Get the biggest one you have room for. Once you have a freezer you will use it constantly and then find you don't have room, and the larger ones don't use much more electricity than the small ones. I have a 15 cu ft (4' long) and wish I had room for the 5' size. Mine came with dividers that you can use to section in 4 parts and then 2 baskets that slide back and forth. VERY useful. (Actually, mine was on backorder and I got a free upgrade with the organizer goodies. Mom uses large pieces of
cardboard to section hers up; same principle.) So I have a section for
beef & bison, poultry & fish, pork and bread and then other non-meat in containers, then I use the baskets for bags of vegetables, boxes of butter, etc. There's another shelf (over the compressor) that usually has the jugs of water I use to fill up any empty space.
Either Frigidaire or GE is good. GE doesn't make their own freezers; they outsource it. (Haier, I think). Frigidaire makes most of the house brands like Kenmore, so as long as you don't go for a bargain basement knockoff you are probably okay to shop on price.