It makes you wonder why they even bothered to release a disk version anyway if all of the machines had cartridge ports and the XE version was compatible with almost all of the machines out there.
Some XE games will work fine with the 800; others require more RAM.
It's been a while since I had my 800 hooked up, but I just tested the Star Raiders II cartridge in Altirra, and it worked just fine with the 48K Atari 800 profile.
If the Atarimania dates are to be believed, the disk version actually came out first in 1985. The cart version probably came out when they were looking for new carts to release for the new XEGS system in 1987.