The difference is...

I just purchased the 99 SR5 4x4 (highlander). It is pretty much loaded (all but leather and the new fulltime 4x4). The new fulltime 4x4 offered only on limited is just that...fulltime 4x4. No switching between 2wd and 4wd and yes that means driving in 4wd on dry pavement. Personally I prefer the "on the fly" switch from 2wd to 4wd. It's a proven function and works very very well. At times when I need the 4x4 quickly from 2wd I make sure my speed is below 25 and an easy smooth shift is all that is needed and instantly I can feel the front end pulling. I would want to see this new fulltime feature get some exposure and real time experience before I would consider it. Besides why change something that works great anyway? All for the extra convieniece of no shifting? Big deal. To me it's not worth the xtra $1500. Stick with the tried and proven. Less headache down the road and less to come out of your wallet.