I built shop in 1995 and put in 2 Rotary 9000# 2-post lifts and a 12,000 ALM 4 post drive on lift. I did extensive research before making the purchase and found lots of differences between the manufacturers. The biggest issue with the 2 post lifts that I had issue with was the type of pad / pod that contacts the vehicle to lift it. The rotary uses a cast design that will stand up or lay flat and you can also get a truck adapter that will make it another 4" taller or so. Some of the lesser quality lifts use a pipe with a pad on it and they are somewhat unstable for working on a vehicle in my opinion and experience. The 4 post drive on style lifts have many different designs for the safety locks. Be cautious when purchasing a lift that you plan on standing under to work and park another car under. Some don't have a very positive locking method nor very strong from what I've seen. You should also look at the cables and pulleys that raise the lift on a 4 post, again lots of design differences and remember your life is going to be underneath it. The last issue to watch out for when buying a used life is to make sure that the cables, latches, guides are all in good order. I got to be good friends with a guy who worked on and installed lifts and he recommends that cables on a 4 post used in a commercial shop be replaced after 10-15 years of service. Bottom line with lifts, be safe.
Don
