What is so hard about copying to a flash drive? If you had to get mods via the PSN store then Sony would have to approve them.
As for if mods are the only thing...
There's always keyboard/mouse support, installing the game on the hard-drive to make load times extremely short, the massive map collection that Epic stated won't all fit onto DVD and the fact that the port was done incredibly well - with everything looking fantastic and running buttery smooth. If it will run as well(or better?) on the 360, I don't know, but Technically speaking the only game you could compare it to on the 360 is Gears, and it doesn't have Gears frame rate dips, while it has way way way more on screen and things happening much faster.
As for if mods are the only thing...
There's always keyboard/mouse support, installing the game on the hard-drive to make load times extremely short, the massive map collection that Epic stated won't all fit onto DVD and the fact that the port was done incredibly well - with everything looking fantastic and running buttery smooth. If it will run as well(or better?) on the 360, I don't know, but Technically speaking the only game you could compare it to on the 360 is Gears, and it doesn't have Gears frame rate dips, while it has way way way more on screen and things happening much faster.