It's a case of the ultimate lazy port, as it was just farmed out. As much as I LOVE the Half Life games, (HL2 is still my favorite FPS of all time, and Ep 2 is great,) if I had a friend who only had a PS3 to play the Orange Box on, I'd have to advise against buying it. That's just sad.
It's also a case of the 360 version being dramatically over-rated IMO, as Team Fortress (which was one of the most highly anticipated pieces of the box,) has such terrible lag that it is damn near unplayable online compared to the PC version. It just pisses you off when you try to play it.
Sure there are a lot of other games there in the box, but TF's online was a key component for for many 360 consumers like me, and it turns out that it sucks online. Seriously, any reviewer that gave the 360 version of Orange Box a super-high score with that key title in the box so miserably flawed, was either paid off, or an idiot. They did their readers no favors by overrating the game in the face of such a crucial flaw. No f---ing way it's GOTY. It's gimped, therefore, it isn't even in the 360's Top 3, IMO.