I fly quite a bit. Mostly shorter flights around the West. I tend to gravitate towards the small jets. You get on and off them quickly. The only downside is they tend to be the Canadair Regional Jets. What I call the "hang over" flights. No matter what your size, you always seem to hang over the next seat, or into the aisle. And you tend to bang your head. But if you can keep the flights under a couple of hours, it's worth it.
The big jets just take a lot longer to load up and get off. But you do get more room to walk around. For me the ideal jet would be one which had some room, but was easy to load and unload. Now Southwest has taken that to an art form, but I just don't get excited waiting in those cattle chutes to get on.
Today I flew back from Chicago on a Delta code share flight and did I get a pleasant suprise. They were flying an Embraer (Brazil) 170. Same number of passengers as the Canadair plane, but the seats were larger, and you could stand up in the aisle. No more hangover. And the seats were comfortable and the cabin was good looking. There even was a first class section. I'm not sure of the economics of this aircraft, but I would switch airlines to fly on this airplane. (I do think Jet Blue is going that way.)
Now if only Travelocity had an option to pick the aircraft............