In my opinion, the major thing is that tegus are better looking than monitors. Tegus are better behaved. I have yet to have a tegu poop on me when I pick it up, but I've had many a savannah empty their entire bowl system on me.
The monitors get really long and get a lot bulkier than tegus. There's a whole lot of different species of monitor with different qualities to them. In my experience, I find tegus to be a lot easier to work with than monitors.
:What is the major diffirence between a monitor and a tegu? Thanks in advance.