FRONT DRIVE: best climber
CENTER DRIVE: most maneuverable
REAR DRIVE: easiest to steer, but least maneuverable
Center (mid-wheel) drive is the one with the smallest turning radius which brings it closest to "turn on a dime". It is great indoors for this reason. BUT, in a small space where you have to back up and go forward again to get the chair lined up where you want it (such as straight on to the sink, computer, table, etc.) the casters will cause really bad lurching to the side as you back up and move forward.
When my 10 year old rear wheel drive chair needed replaced, the mid-wheel was ordered for me. I can't get it up to the bathroom sink, my computer desk, or positioned in the van without repeated attempts and damage to walls, woodwork, or furniture. Outdoors it gets hung up on uneven surfaces with the casters holding the drive wheels up off the ground spinning uselessly. It has to be driven sideways up the driveway curb or the same thing happens. My old rear wheel drive chair had none of these problems! Even though it couldn't turn on a dime, it was easy to back up a little and complete a tight turn -- without bashing furniture and nearby ankles.
I was horrified to find that a ten year newer chair was far inferior in maneuverability to a ten year old one. I am currently engaged in a battle to get a rear wheel drive chair instead.
Also, if you expect to use BiPAP or a ventilator, don't go with any Quantum brand. Nice chairs but the position of the tilt and recline mechanism on the back of the seat forces the BiPAP or vent to be mounted so far back that the length of the chair is increased significantly. That makes it hard to get into smaller places such as bathrooms and elevators.
See my website at
ALS: From Both Sides for more info on choosing and ordering a chair.