The specs for both first:
PS3:
http://www.ps3power.com/ps3hardwarespecs.htm Wii:
http://wii.nintendo.com/hardware.html Graphics: The PS3 has this one. It's more powerful thanks to the Cell Broadband system which let's it do more as far a graphics go. Though if you'r hoping to use your HDTVs you will have to buy extra hardware since it doesn't ship with the neccessary HDMI cables.
Controls: Both have wireless controllers and motion sensing but the Wii-mote does allow for a wider range of motion rather than the two handed PS controller. The Wii-mote also has a rumble pack, built in sound, built in memory and peripherals like the nunchuck, zapper and, controller glove (POWER Glove! ... sorry. Force of habit.) that will provide a much more interactive gameplay.
Games: This one's a bit subjective. As far as the release games go The Wii seems to have a launch stable directed toward the whole family (Everything from Orchestra to Zelda to Splinter Cell) where the PS3 launch titles are mostly rpg and action/adventure (I'm including the FPS's in this) type games with a few fighting games (Tekken and EA Sports Fight Night Round 3) and driving games (The Getaway and Formula One). It's good for getting the usual gamers but the problem is with the exception of a few games like MGS and FF XIII alot of the games are also on the cheaper X-Box 360. Except for the hardcore FF and MGS fans there won't be a big draw if the gamer has a 360. The wii has an upper hand in this because alot of their games feature a new, more interactive, gaming experience and it comes bundled with a game when you buy it.
Price: PS3: $500 - $600. Wii: $250
Backwards Compatability: From what I've read the PS3 will be backwards compatible with PS1/2 games so that's a plus for them. The Wii will have the Virtual Console which will allow gamers to purchase older games cheaply from all of their systems as well as some sega games as well. The disk drive for the Wii will accept Gamecube disks as well as DVD disks which is a first. For gamers who just want to play their older games on a new system without buying anything the PS3 has the upper hand. For the retro gamers though the Wii is the better choice. The Virtual Console will start ot with 30 games at launch and they'll expand from there.
Other Media: The PS3 has this one. It plays Blu-Ray, DVD, and CDs that's hard to beat. The only problem is that the HD features won't work without having to buy extra cables. The Wii will play DVD's but it will require an attachment to do so.
Online Capabilities: Both will have free internet access however the PS3 doesn't have a browser that I've heard of. The Wii will have the Opera browser. Both will also connect wirelessly to their handhelp counterparts (DS and PSP) The Wii will also have their channels which will include their Mii chanell which will allow player to create customizable avatars that they'll be able to use in some games.
That's all I can think of right now. If I missed something please let me know. I may edit more in later.