360 is my favorite of the 2 consoles, since it appeals to me more, however the PS3 really caught up and at this point is the superior investment.
If you're going wireless for the 360, you practically need the adapter. It's got the best connection with the 360. I've tried other forms of wireless but only the adapter worked for me. The thing is, I can't have a cable. A lot of people don't have their system and computer in the same room, so wired is not an option.
If you do have wired though, the price is still pretty close:
Pro + Wired Cable (let's say $30) + 1 year of XBL ($50) = $380. Plus with a possible price cut soon (let's be honest though, it is going to happen), the PS3 will be slightly cheaper. Point is, price is not really an argument anymore, so if you add everything else up, the PS3 is superior at this point.
Really though, it comes down to opinion, so pick whichever ones you prefer. Here are pros and cons:
Xbox 360: Pros- Superior controller (particularly for FPS), high-quality shooter, RPGs, superior downloadable service, better overall online (though you have to pay), slightly more variety
Cons- RROD is a problem if you buy a used/refurbished console (make sure the one you buy is new and made past August 08), you have to pay for online (not that much though, you just buy 1 less game a year)
PS3: Pros- Superior and larger variety of current and upcoming exclusives, blu-ray capability, free online
Cons- Online weaker then 360, blu-ray DVDs cost a ton of money, weaker downloadable service, receives many downloadable games and content later then 360 users

), has great exclusives (Banjo: N&B, Dead Rising), has tons of great games on XBLA, It's cheap, and the new Jasper chip has fixed it's technical shortcomings tremendously. The downsides are that it has no built-in wireless, the online has to be paid for, and though it has great exclusives, there's not a lot of "true" ones. Also the required Microsoft avatars are ugly.