We get a lot of questions here about which Vibram Five Fingers are the best. I am admittedly a Vibram newbie; I started running in them about 5 months ago. I have started a small collection (KSOs,Sprints, and Bikilas) and luckily my job allows me to talk about them all day long!
Vibram Five Finger KSO
These were the first VFFs that I got, and I believe this was a great decision. I can do anything in them, from kiteboarding to trail running. Mine are black, which does get a bit hot, but besides that, I love them. I run mainly on trails and I think these work splendidly. I have a good feel for the ground but don't have to worry about getting stabbed by sticks.
Vibram FiveFinger Sprint
When I decided to do a triathlon in VFFs, I needed something that would be very fast to put on. I initially thought that I would go with the Classics, but the rubber on the heal is not the right angle for me, resulting in blistering. I should say, a co-worker has them and would not trade them for any other shoe, so perhaps it is just my funny achilles. The Sprints were fast in the transition and they are great for hot days, when more airflow is better. For short runs in debris-free areas, I definitely wear my Sprints.
Vibram Five Finger Bikilas
I am training for my first Marathon and I have definitely put the Bikilas to use. I usually run on trails, but the Marathon is on pavement, so I have had to make the switch. When I was running predominantly on trails, I never understood why someone would go with the Bikilas over the KSO, as the Bikilas do feel less barefoot. After pounding the pavement, I get it! We evolved to run barefoot, but we didn't evolve to run on pavement, so that bit of extra sole really made a difference. This is where I should admit I do not have the best of form (I am sure that there are lots of barefooters who can run in KSOs on pavement no problem), but the Bikila has really eased the transition from running on soft, cushy dirt to solid pavement.
I have obviously left out a lot of shoes, as I only have experience with three of them. I can refer you to the website that is my go-to, birthdayshoes.com, where you can find hundreds of articles and threads about all things Barefoot and Vibram.