A decent package here, an astounding package elsewhere. Long read, but do yourself a favor before settling for less.
The Source engine has come a long way with updates coming out every few months or so. Everything about these games from the textures, physics, and annoying glitches have been worked to near perfection and provide a much more enjoyable experience on the PC. It may not seem like a big deal on paper, but when you consider this on top of the huge modding potential of the games and better controls, this version just doesn't cut it. Almost any decent PC can run these games and if you have doubts, download the HL2 demo and mess with the settings. Now that that's out of the way, we still aren't done here. This is only half of it.
Even if none of that sounds important and you still think this is the Orange Box for you, there are updates to consider. Tons of them. Portal has received a small update that involves radios that lead to hidden images, but that's not the deal breaker. This is mainly about TF2 where most of your time will probably be spent... and it's NOT the same game on each platform.
Being a purely multiplayer game means that Team Fortress 2 relies on it's community and updates by Valve to keep it alive. This simply doesn't exist anywhere but the PC. Days before this review the game was given a Medieval, melee only mode with a new map, tons of new weapons to suit your playstyle (bear claws for the Heavy, a rake for the Pyro, etc, all with new stats and models), and new hats which are mostly just for show but still add to the fun. More was added weeks before that, even more months before, and so on. Special themed updates also roll around on Christmas and Halloween. This has gone on for years and what we're left with now is a game so full of modes, maps, customization, and unique weapons that it's almost impossible to run out of things to do. If you wind up hating the new items and stats, find a server that disables them and keep your game modes and maps. The best part? You don't pay a single cent for any of this (unless you want to buy the weapons and hats) outside of what you initially payed for the game, which frequently goes on ridiculous sales anyway.
The bottom line is that if you absolutely need to play HL2 and Portal but have a horribly bad computer, this is just "okay". If you want to play the slightly updated versions of these games and the version of TF2 full of options and still receiving love from the developers, get it on PC.