We have had a VP215 for a little over 3 years now and it has been a workhorse for both my much better half and I for all types of food. For our purposes, the trade of relative portability (VP215 at +/-85lbs and VP321 at +/- 200lbs) for additional chamber size and/or dual sealers was a game changer ... we keep the sealer on wheels on the floor and it is easily rolled out of the way (and out of sight) in a corner off our kitchen when not in use. The reality is that, contrary to our initial intentions, she uses it more than I so movability and ease of use for her purposes has been really important. The machine has operated perfectly and we haven't had a seal fail to date either during freezing or cooking (sous vide).
If weight and movability wasn't an issue, the larger machine would be a bonus on the few occasions that we do really large batches but then our question would be whether to get the 320 (single seal bar at the front of the chamber) or the 321 (double seal bars at the sides of the chamber) given the rectangular chamber shape and the dimensions of the bags we normally want to seal.