For my '04 2120, I went with the 150 carb 2 stroke. For us, it's been just right. With 3 other passengers, it still gets on plane quickly enough as the trim tabs help out. At speed in the bay, I can keep up with the crowd headed to the fishing holes. But lets face it, it's certainly not a go fast boat. Heading out of the inlet when I hit the wind and current head on, there's ample power to get past the jetties and swells into the clear.
Someone here can probably verify this, but I think the 2120 is a deep-v. The formal model identifier I find on my boat is "2120DVSC". I'm thinking (right or wrong) that the DVSC is the code for 'deep-v,sport cabin'. That might help gauge if more or less HP is better for this hull. But like it was mentioned, test ride them if you can.
John S.