I have a few 4 posts.(
http://www.kennan.ab.ca/lifts.html ) Local dealer.
Mostly for storage, they work great. The casters supplied are shat and don't roll with it loaded. Besides that no complaints.
For working on the car I think I like the two post a little better. Being able to move the lift was a big priority for me so the four post became a obvious choice. Have yet to run into a situation working on a car that I thought they sucked?