QTI is very capable and will get you most places you'll ever try to go.
However it is not as capable as QDII. Just yesterday I was out wheeling and found a few obstacles that my friends QTI system just couldn't transfer enough power to make it up a very rutted climb. QDII in 4-low was no issue.
2007 Jeep Commander Limited, 5.7L, QD-II
too many to list. Check out my garage
My Garage: Click Here