Ive using a 4 post Challenger and a 2 post Bend Pak in my shop. If you plan to use the lift for stacking cars, the 4 post is definitely what you want, just because you dont have to set the posts under the vehicle, you can drive right on it. If you plan to really work on the car alot while its up in the air, I would strongly recommend a two post, as the ramps prohibit pretty much any suspension work, and always seem to be in the way unless your working in the middle of the car. If you have the jacks that slide down the middle for your 4 post, then you can do suspension work, but the ramp still always seems to be in my way when im using the 4 post. With the two post, setting the posts underneath the vehicle will take less than a minute once you know where they should go everytime. Im 6'3" and yes my 4 post goes high enough that I can stand up completely underneath it, but I barely have to tilt my head to clear on the 2 post. Anyone 6" or less should not have a problem with most of them that are on the market. If you plan to work on cars as well, make sure the height when all the way down is as low as possible. The bend pak I use is 4" and can get under a stock ride height gen 2, and my lowered 2" SRT4 without any problems. Also make sure it comes with truck adapters if you choose a 2 post. Thats my $.02,
Justin