[chrismorse]

I'm very happy with the Rotary twin post, asymmetric.
As others have said, Used can save you a bunch. I talked with my local FLAPS and learned that a local independent shop was closing and i went down and talked with the owner, I offered $1000 cash. They took it down and helped load it into my truck.

In particular, i like the ability to walk under the car/truck without ducking or having to scoot or crawl under it.
Additionally, (as has been posted), there are two basic types, top bar and bottom cross over. The bottom cross over allows nearly unlimited vehicle height to lift, BUT, it is a constant annoyance, a tripping hazard, makes it harder to roll cars in or out, could be in the way of a trans jack or adjustable support post and it makes clean up a bit more difficult.
The top cross over has the automatic stop bar that keeps from the car hitting the cross bar, or roof/ceiling framing.
I would opt for the 14 foot height, so you can lift vehicles with the hood open, as i just did with my wifes benze, which has the ability to open the hood straight up, (so i could install a chain fall to lift the head assembly off).
Don't forget to allow room for an overhead door, tracks and opener. Doors, hoods, campers and lumber racks on trucks need room to get the vehicle to full height.
I lucked out and had a three bay garage, with 10 foot plates and scissor trusses, I still had to move the opener and track up for clearance.
Another consideration is placement. Give yourself a bit of extra room for walking around the end of the vehicle and extra long vehicles.
I would recommend additional concrete footings under the post locations and an extra few bars of #4 or 5 reinforcement.
Finally, thinking ahead, you could run the main power, air lines or additional electricity to power up tools - in the concrete, at the post location(s).
My concrete floor was not reinforced and had a few cracks, so i cut out a 10 x 12 foot section, dug footings, doweled into the old concrete to tie in a new grid of rebar.

chris