Agreed with jonny1989. It depends on the games you want to play. PC-only or originally PC games generally look better on the PC (and the graphics power is much higher on the PC). However, console ports to the PC do not look as well as when it was on the console. And like jonny1989 said, you won't have to worry about hardware upgrades to play games. There will always be games to play for another good 5 years or so.
I personally would get a PS3, though. You hardly ever hear about them failing, and IMO it's an overall better console. The hard drive is cheap and easy to upgrade (don't even have to dig into the console, they provide a door on the side lol), and it has a Blu-Ray player already installed. You have to buy the HD-DVD/Blu-Ray player for the 360 (they're getting rid of HD-DVD and introducing a Blu-Ray player for the 360). The Playstation Network is free too and not all that bad, and obviously internet, DVD-upconverting, etc etc.
But I'm biased, I own a PS3 40GB lol! My friend has the 360 and I just wasn't impressed.
With the PC, though, you get better graphics and higher resolutions (PS3 is 1080p 1920x1080 on a handful of games right now, and mostly 1280x720 720p). But again that boils down to the game you're playing.
If you can at all, I would keep both. I have both my PC w/ only an 8600GT volt-modded and overclocked, and my PS3, and I like to play different things on both. The 8600GT is about on par with the PS3/xbox360 graphics at 720p, and on games like Prey and HL2 I can play at 1080p with full AA/AF, and it looks AWESOME compared to the PS3.
You really can't go wrong with either, but the PS3 is less complicated and the PC has more expandability (more $$$) and overall better graphics, again depending on the game.
EDIT: It's very difficult to compare the two, because they're two totally different genres. Games are developed for consoles based on the current hardware (console), and nothing else changes. It's the same hardware. However, in the PC gaming world, hardware is changed and updated based on the games that are developed...it's backwards compared to consoles. New software that is more advanced and uses more features is developed, and hardware is updated based on the new software. Comparing one to another is like comparing apples to oranges. They each have their benefits. Consoles cost less money in the long run, and are "plug and play" and, nowadays, offer a plethora of features that, for the money, is hard to beat, and less complicated to get set up. But if you're up to the challenge of getting a gaming rig setup, it has its own benefits, although it will almost always cost you more in the long run. Especially if you are the type that has to have the "latest and greatest" and want to game at extreme resolutions and everything has to be perfect. I opted for a little of both, a moderate gaming PC and a console. I don't have to game at the highest resolutions and have all features set to high, and enable this and enable that. The budget build suits me just fine. It seems kind of ridiculous to spend $1,500 in hardware just to play a $30-50 game smoothly. But that's what some people are into, nothing wrong with that.