The 1 and 2 are more casual, like mel says. You squeeze or push and snap. Very fast, not very repeatable. The 3, I've never used or seen it used, is more deliberate and repeatable - you move the balls on the antennae to position it just so.
If the 3 doesn't allow the squeeze and shoot technique, I'd want both the 3 and the 1 or 2.
I bought the 1 for two reasons - I like the effects better, it's more extreme than the 2, I think both sharper and more blurry. Oh and it's cheaper.
A couple of times a year I go out for a day with just the lensbaby. I'm quasi ambidextrous so perhaps it's easier for me to do the peace sign focus technique.