When you open the door on an upright, cold air spills out from the bottom, while warm, humid air sneaks in at the top. That makes the freezer work harder (and use more energy) to stay cold, and temperatures may fluctuate a bit. Self-defrost models compensate by using a fan to circulate cold air from the cooling coils, which are in the back wall.
Manual-defrost uprights don't have a fan to circulate cold air. That can result in uneven temperatures. Optimally, a freezer should maintain a temperature of 0° F throughout. Like refrig/freezer combos door shelves on manual-defrost uprights can be 15° to 20° degrees warmer than the main space. That's unacceptable for long term storage.
Since you already have a freezer in you fridge plus a chest type, I assume you'll be moving stuff into your refridge freezer as you use it. That makes things getting hidden or forgotten in the chest less of a problem.
