Edit - I forgot to mention that the PS3 has far less hardware reliability issues than the 360, although the newer 360's are slightly more reliable than the old ones. This should be an important consideration for you.
Well it looks like the Arcade is not an option at all for you, so we will just leave that out.
To me, based off what you want, you have 2 main options, the 80 gig MGS4 bundle or the 360 Elite.
The $500 80 gig comes with a game, which is a plus, especially because it is arguably the best PS3 exclusive, but it doesn't have component or HDMI cables ($20 and less than $10 respectively). You also get a Blu-Ray player which retails for around $300 by itself. The PSN is free, which will save you a lot of money. XBLA has slightly more downloadable titles though. The gap is much smaller than it used to be, however. You will have full backwards compatibility with PS1 games and about 70% compatibility with PS2 games (most major 1st and 3rd party games included in that). The 40 gig (or new 80 gig) has no BC. You also have a built in wireless card, which is a BIG plus.
The $450 Elite has a slightly bigger HDD (unfortunately you can't store your video files from your PC on it though, which makes it MUCH less useful). You also save $50 to begin with, but you have to remember that you are probably going to need a Live subscription, which is $60 retail price. You will have to renew it every year too to play online. You also don't get any games with that. You do get an HDMI cable in the box though, but those only cost about $10. You do get a headset too. Plus you get to stream Netflix (can also be done on the PC). A wireless card will cost you around $85-100, so you better have an ethernet port near where you are going to hook it up or be ready to pay extra.
To me, the 80 GB MGS4 is a slightly better deal. You get a game, you don't have to pay an online subscription, and you get a Blu-Ray player, not to mention built-in wireless. You wont be able to stream Netflix though (selection is still pretty small in this point on streaming). At least you can always use the Netflix subscription without a 360, but you won't have a Blu-Ray player if you buy a 360.
We had two bags of grass, seventy-five pellets of mescaline, five sheets of high-powered blotter acid, a salt shaker half full of cocaine, a whole galaxy of multi-colored uppers, downers, screamers, laughers…Also a quart of tequila, a quart of rum, a case of beer, a pint of raw ether and two dozen amyls. The only thing that really worried me was the ether. There is nothing in the world more helpless and irresponsible and depraved than a man in the depths of an ether binge. –Raoul Duke
It is hard to shed anything but crocodile tears over White House speechwriter Patrick Buchanan's tragic analysis of the Nixon debacle. "It's like Sisyphus," he said. "We rolled the rock all the way up the mountain...and it rolled right back down on us...." Neither Sisyphus nor the commander of the Light Brigade nor Pat Buchanan had the time or any real inclination to question what they were doing...a martyr, to the bitter end, to a "flawed" cause and a narrow, atavistic concept of conservative politics that has done more damage to itself and the country in less than six years than its liberal enemies could have done in two or three decades. -Hunter S. Thompson