Depends on what you want, and where you camp. A deeper slide will more often than not render the camper useless with the slide in, as it usually cuts off one end of the RV. Usually the end with the bath. Also. You have to- move over farther in the site to keep from sliding out into your camping neighbors site. Remember. You site ends at your sewer hookup. NEVER slide out past it.
A more shallow slide usually allows you to still use your camper IF your site is full of trees, and there is no room to slide it out. Have had that happen in the mountains, and once at the beach. It also lets you have more room on the door / front side of the TT where you spend your time.
So you see, it is all in what you want.