<RANT>
Both fucked up in many ways.
TF2's gameplay is utterly retarded mainly thanks to these idiotically long respawn times, let alone the freakin' slow walkbacks - totally ruins the gameplay and it's a big loss for me because I was very excited ever since the first trailers... screw it, Valve, never gonna buy any of your utter boxed crap again.
ET:QW in reality has
nothing to do with Quake. It bears something from ET - which I never liked - but at the same time it tries to imitate BF - which was utterly slow for me - and the attempt to create two distinctively different races ended up in baaaaadly unbalanced game. You don't really feel it in the demo but in the full game it's more than obvious; SD screwed it royally.
Besides this Splash Damage totally fucked up the vehicles - seriously: nobody from SD every played UT2k4? Check those vehicles: simple, stupid handlilng model BUT IT WORKS VERY WELL. This one SUCKS. BIG TIME in case of the CHOPPERS regardless of Advanced controls are enabled or disabled.
The red triangles above the enemies' heads ARE RIDICULOUS - the person who figured this will be good is obviously utterly and pathetically clueless about online FPS gaming. What kind of retarded things is this? KILLS THE WHOLE GAME.
These are the biggest idiocies in QW but of course, there are other meaningless stupidities like completely unnecessary long waiting before respawn, the rather dull graphics - imagine it a year or 2 years from now: it's going to look butt-ugly! Look at Ut2k4 today... Crysis MP beta kinda sucks too but at least it has decent graphics options - QW is just dull, thanks to id's fucked-up D3 engine though SD deserves a kudos making possible big, open areas instead of the shitty Doom 3's boring and craptastic corridor shootings.
</RANT>
So after all if you REALLY wan to pick from these two go with TF2 - for me it's a total crapshoot, a fuckin' annoying crap gameplay, I stopped playing it after 3-4 hours total and I'm still playing QW - just got my game tag fixed by Activison - but most of the people will be much better off with TF2 - it's at least funny, has a avery distinctive style and characters are great, teams are balanced etc.
If Valve decides to fix all these retarded problems in TF2 then I might give another chance - however I can already see the possibility of putting ET:QW up on eBay or giving it to somebody else very soon... only the date is in question...
PS: did anyone else notice that as far as engines go this round now obviously went to Epic's UE3?

Besides QW I cannot recall ANY tech4 -based (D3-engine) game but QW is id's own game, outsourced to SD (heck, it seems by now id recognized they suck at games as they never been able to make anything beyond mediocre since Doom but that, being a first of its kind, was rather an exception.)
On the contrary UE3 is all over the place: Bioshock, Fury (played the beta), Frontlines (playing the beta), MoH: Airborne, BIA: Hells' Highway (coming), next America's Army (v3.0, next year?) etc just to pick some besides the Epic's own Gears of War and UT3 (both coming before Christmas) and and two dozen or so console games in development. I can see why Carmack was already pushing tech5 at last WWDC...
PS2: UT3 demo is downloading now... fingers are crossed... this year only brought disappointments so far (sans Bioshock, it's great!), UT3 is my last hope...