Wii is more fun but theres one thing you get with a PS3 thats so worth it.......
[size=20]BLUE RAY!![/size]
If you have a HDTV you will love BR films
Getting my PS3 this week and then for xmas a wii 
I have a perfectly good media center, that can do Blueray. Cheaper than a PS3 as well 
MCE (or VMC) also does one of the best upscaling from std DVD to 1080p I've ever seen. Only film I own on both std DVD and BR is Casino Royale, and you'd be hard pressed to tell them apart. Yes, the BR does have more detail, but from 10ft away in your armchair, you wouldn't know. Thats how good MCE/VMC is at the upscale
What size is your TV?
40", mce running 1920 x 1080. LCD
True but isnt the PS3 BR reader firmware updateable to the next version whereas very few dedicated BR players are.
I had XP MCE running on my last system and it kept crashing, losing the channel data, etc so generally not impressed although the conceptual idea was brilliant. Now I have Sky+ I got rid and now have Vista on it and turned it into a gen dogsbody machine (stopped it crashing.....)
Sadly for those who bought BR players, Sony changed the spec at a hardware capabilities level between BR revisions. Its unlikely they will make the PS3 incompatible, well not until PS4 out (rumoured 2010).
Even with XP MCE, I never lost channel data :-/. XP MCE problem is it needs about 2 reboots a week if used heavily (XP ain't great constant in and out of standby, nor usb power management).
With VMC, only repeated problems I get are TV tuners sometimes get lost after coming from standby (its always one of the Haupauge dual tuners - I have 5 tuners in mine) which is hardware issue, the display (frontapanel) driver sometimes errors resuming from standby, requiring you to hit OK, and very rarely, IR controller stops responding at software level.
Unlike XP MCE, VMC I very rarely restart.
The big thing that breaks MCEs is installing those gay 'codec packs'. Only 1 extra codec needed for VMC, thats ffdshow. For hidef, if the film is in a wrapper, you need the unwrappers as well.