360 for the games, PS3 for the media playback.
Most of the time I will only buy games for the 360, unless the company really really wanted you to do otherwise. It's the standard console for game makers, so expect it to be the best for getting titles. Xbox live is great, but costs, and the costs rose 10 bucks in the past year. That being said, the community is stronger, but, there are far too many punks online who want to leave you irritating, offensive messages, and you have little recourse in order to defend yourself, while their anonymous behavior has compromised your experience. The difference between the graphics for the two systems is not dramatic if noticeable at all, oddly enough. Most games look the same, operate similarly, but from time to time have certain features missing from one console version to the next. Some game companies are far more loyal to one system or the other historically, and will thus not update as often, leaving certain expansions or features behind in one of the consoles. So, sometimes, it pays to look at what you would most want to play.
If you want Netflix with it, yes, you will pay more because of Xbox live. I also consider the Netflix application to be far worse than the PS3 version. If your connection fluctuates often, or even sometimes, the app will cut off playback and then give you a loading screen in order to reload the content. The PS3 app does as little of that as possible, and attempts to do it on the fly, though occasionally, if you are hitting a dead end, it will throw a loading bar on the bottom of the screen (while still having the content at a freeze).
As a media player, the 360 isn't ..bad..per se, but it is immensely irritating that it relies on Xbox live for darn near everything. You can listen to music while playing the game (can't on the PS3). If you are offline, or the xbox servers are momentarily down, guess what, sometimes you won't be able to play your files, because you clearly need to use Xbox live servers to play a movie on your thumbdrive. I have also had plenty of trouble dealing with so-called "optional media updates" which tend to not work and force me to redownload them to get access to MPEG-4, AAC, H.264, etc. So, just in case something goes wrong, and I have no internet, and want to do something other than games, sometimes that's a no-go! *smacks head. Also, the Shuffle music option is beyond ridiculous. Worst implimentation ever. I remember hearing people bitch and moan about iTunes "shuffle" usually playing music that was listened to most. Well, the worst thing about the 360 is, it doesn't play the stuff you listen to the most. In fact, it picks a letter in the alphabet for an artist, and only plays that until it is done. So, last night, S, was chosen. Scott Walker and Smashing Pumpkins was the only thing I heard last night, despite having on my Top Rated Playlist over 2000 songs, and on the full library, 15-16 thousand tracks. The Xbox didn't care. The letter S was what I was going to listen to that night. You can, however, play playlists quite well, so if you choose carefully (ie. small number of tracks), it should be just fine.
The playstation 3 as a gaming device is usually fine. Decent game selection, free internet gaming, and so on. However, despite the fact I rarely do this anymore, the sense of community is less, because the playstation gamers aren't constantly told about microphones and headsets. So fewer people have them. This can be a good thing (previous example with irritating people), or a bad thing (if you want to be social). The games actually do "installs" on the hard drives, and this can be a set back if you want to "go, go, go!" and not have to wait. You cannot listen to music while playing most games. You rely only on the game. It's stupid, but true. There are a select number of games that allow you to do this!
The PS3 is a brilliant media player, but I have issues nevertheless. First and foremost, I'm not a folder-driven sort of fellow. This means, if you have a drive connected with media, you will be operating under the assumption you navigate everything through folders, rather than a simple "Artist" "Album" "Playlist" option like you can through the Xbox. If you have a Mac-formatted iPod, don't bother. It can't read that. You can still, however, play a great many codecs without much hassle (don't require Playstation Network access to play the files, cough cough), and you have yourself a solid blu-ray player that will mostly be future-proof. It's strongest suit as a media player is simply that it does not act like an Xbox. I absolutely despise watching stuff on an Xbox, and nearly dislike it entirely for listening to music, if it weren't for the irritating folder navigation of the PS3.