If you can spare the space and extra cost, get a 4-post. Otherwise get a 2-post (a clear-floor design). I have a 30x40x12 metal building. I went with metal because the wood frame had trusses that would interfere with a lift. With a 2:12 pitch, I should be able to fit one of the wider 12' lifts with a few inches to spare. The relatively small 30x40 work space limits me to a 2-post. But I can store the arms up so the only obstacles would be the posts. You could do the same with a 4-post, but you'll have 4 posts in your work space that will seem to always be in the way.
As far as brand/model, it generally comes down to either the cheap Chinese knock-offs or the high-dollar big name brands. I never found any reports of injuries or deaths or even any major failures from the Chinese lifts when I was researching this a couple years ago. They seem to be plenty solid except for some of their wear parts wearing out much faster than they do on the big name brands. For non-commercial use, I'd say they're ok. There are some more established name brands that are actually certified. I don;t know where all my research notes went to or I'd share. I still keep my eyes open for a Bend-Pak, Rotary or Challenger being sold from a shop going out of business. Or, better yet, a State auction. The LA DOTD maintenance department is required to replace their lifts every few years. They use stuff like Mohawk and Bend-Pak and they maintain their equipment just as well as their trucks. I'm never in a position to spend when they have the State auctions, though.