Chest freezers are more efficient, probably because all the cold air doesn't fall out when you open them. Before you buy anything, look at the rated annual power consumption (kWh/year) and multiply that out by your electricity price to get running costs. If you live anywhere like I do and pay 30c/kWh, those numbers will start to become very important to you. Here in Adelaide, it's not really worth stockpiling huge amounts of frozen film unless you know for certain that there is about to be a big price rise. My freezer has about 30L of film in it, the rest is bulk-prepared food - make a massive batch on the weekend, freeze portions and then nuke for gourmet dinner each weeknight,
My chest freezer uses 225kWh/yr, which is $67. If I had gone for the upright model of similar capacity, it was 400kWh/yr, or an EXTRA $50/year just to have the door on the front. In other words, my freezer is eating three or four 5-packs of film in electricity each year; I don't want to feed it six!
Now factor in the 15% per annum growth in electricity prices.