A standard 4 post 9000 pound lift requires about a 3 1/2" thick, 2500 psi concrete floor. Most modern garage floors are poured with 4" 3000 PSI concrete, so a 4 post lift will not overload it. When in doubt, check with a structural engineer.
I prefer the Bend Pak 4 post lift because they are American made and the company has been around for 35 years, so I am inclined to believe that they will be around for a long time to come. This is important, because you want to know that you will be able to get service parts should you ever need them. It is a lot easier to get parts from an American company than to get them for a lift that was made by an unknown company in some far off land such as China.
I purchased a Bend Pak HD9 four post lift that is presently in transit from the manufacturer in California. It is expected to arrive some time next week. Once I get a crew together we should have it assembled in a few hours.
I have compared the Bend Pak 4 post lift with the Rotary 4 post lift and they appear to be identical in every detail. Rotary doesn't offer a 4 post lift that is under 12,000 lift capacity, so the Rotary was "beefier" than the Bend Pak in the cables. All the rest, including the safety locking system were identical in appearance. Also, both brands are certified by a National lift organization, which I don't now if the other brands of lifts are.