80 will be the most "natural," generally speaking.
Also worthy of note is that the telephoto models are more expensive, and the wide angle models are usually at least 2 or 3 thousand dollars unless they are horribly trashed, and even more if they are in outstanding shape. Kind of out of hand for cameras that can only do one thing...and don't do it particularly better than the other options, at that.
If I was set on the idea of shooting TLRs as my only medium format cameras, I would get a nice Ciroflex model F, Yashica, or a similar camera for when I wanted to travel simple and light with a normal lens. And I would get a Mamiya C330 for the other focal lengths. The Mamiya system has the following lenses: 55, 65, 80, 105, 135, 180, and 250mm.
This being said, I do have a Rolleiflex Wideangle in as close to mint as they come without being NOS. I lucked out on it in a local thrift shop and bought it as an investment more than anything. But when I want to shoot wide with a TLR, the Mamiya is what I use.