I have printed 4X5 contacts nearly exclusively in the past, literally hundreds. I like the intimacy of the smaller print. It takes a bit more dedication on the part of the viewer but is worth thier time to really look at the images.
After a bit of practice at making small movements and getting used to the small image it is very easy and effective. It does take practice and the need to relate the straight contact to the one you are working on, kind of an imaginary grid system, to use in placing the tools.
5X7 would be that much easier. It is a bit difficult to do very fine manipulations but the fact it is a contact print somewhat compensates. I find I need to do a lot less work on a contact than an enlargement. Even printing a 4X5 at 4x5 requires more work than the equivalent contact print.
It's worth the effort to learn the process and teh rewards are very fine prints.