there are two main differences that I'm aware of...

most racks for the IT market are more than 30" deep, as most 1RU servers are about 30" in depth. the other thing that is fairly common is for IT racks to use cage nuts. this is an insert that is placed in a generic square cutout on the rack posts, rather than the posts being pre-drilled for 10-32 bolts, which is the standard in the AV world.

the other factors, which aren't always different, as Middle Atlantic has solutions for most of these issues, are such things as integration with elevated flooring systems, rack ganging, cable ladder mating, DC-DC power solutions, etc...