If you ever want to use it for service, get a two post.
When you drive a car onto a four post lift, you STILL have to jack it up by hand to get the wheels off the ramps. The only advantage to the four post is for added parking space, and I can still do that under my two post if need be.
If you want a clear floor lift, you need a 12' 6" ceiling.
The floor plate lifts will fit with 9' 6", but you can't get a big car or truck high enough to avoid lumps on the head.
Later,