I own both TF2 and L4D and play both somewhat regularly (TF2 more than L4D). I've also had no crashing problems with steam, ever. The only annoyance is that if you are in a community the announcements minimize some other games. I'll be playing DOTA on WC3 and suddenly the game will minimize letting me know one of my groups has scheduled TF2. However, few groups seem to use announcements, and you can always leave groups as I think the communities for FPS games tend to suck.
I like TF2 a lot as a shooter. I believe it is an incredibly well designed game, and seems to fit the model of Smash Brothers before Sakurai boinked it.
1. The game is very newbie friendly. A) The game is open for new players. four of the classes: medic, engineer, heavy, and pyro can be played very effectively by new players against those more familiar with the game. Pinpoint accuracy and lightning reflexes are not required to play these classes.
B) Level design is more intuitive. Levels have color themes of red and blue to help you know which side of the map you are on. Arrows guide you in the direction of key objectives. One of the game modes even has a railroad track that you can simply follow back to the action if you ever get lost.
C) It's easy to tell friend from foe and there is no friendly fire to worry about. It's also easy to tell what class people are. Characters are either dressed in red theme clothes or blue themed clothes. If someone is waearing the same color outfit, then he's on your side. Additionally most of the game types pit one team coming from one side agaisnt the other from the opposite direction. Nearly all of the time enemies will be ahead of you. It's like like CS death match where you have to constantly be aware of every angle. Classes are highly distinguishable from one another so you can always tell what you are up against.
D) No more god damn secret snipers. There is a sniper class in this game, but there is only one, and he is largely ineffective at close range. But most important whenever a player kills you the camera zooms in on the killer so that you know who he was and where he was. It can be annoying as a new player in an FPS to not know how you died or where they shot you from. TF2 removes the mystery. It also forces snipers not to camp in one spot unprotected.
2. The aesthetics are bright and comical as opposed to dreary and gritty seen in most FPS games. A) People wear bright colored clothes. There's no entirely dark black camo suits.
B) Characters are drawn in a cartoon style. These eases the graphical burden on your pc and I feel actually looks better than most ultra high resolution grunting, angry faces of many other FPS games.
C) Environment, weapons, and vocalizations are all designed to be slightly comical. The players may be trying to take the game overly seriously, but the character sure aren't.
3. While easy to learn, there is still depth to the game. A) Soldiers and Demomen can rocket/bomb jump and juggle opponents with explosions. Because of the delay attached to their projectiles a certain amount of skill is involved in predicting enemy movement.
B) Snipers are snipers. The same as in any other game.
C) Scouts are about outmaneuvering and keeping a steady lock on the opponent. A good scout can be very scary.
D) Spies allow for a player to prey slightly on the psychology of opponents. Though they do become less effective as player skill rises, they still are fun to play if you enjoy sneak past and up on people.
E) Even the more newbie friendly classes have depth to them that can be explored.
4. The development team cares a lot about the game, is rather brilliant, and very responsive and aware of the community. I think the TF2 development team (many who also worked on L4d) has some of the best design philosophies I've ever seen in a game. I enjoy reading their blog to see how even the most minor details are full of intelligent intent and purpose.
Check out this blog article on lighting in L4D. Updates are regularly fixing exploits and adding new content.
I'd have to know more about your tastes to recommend TF2 or L4D for you, but I enjoy both. I will say that when I'm playing simply by myself I gravitate towards TF2. I can hop on and off a server in TF2 very easily with little commitment when I need to leave, am no longer enjoying myself, or wish to move to a new map. L4D is a game I really only play when I'm playing with friends. L4D requires a longer commitment of time, leaving a game in the middle is generally something frowned upon (though many still do it). Additionally you have 3 other team mates with you, and their play ability as well as your ability to work as a group matter greatly. I find it very unfun to play with an uncooperative and unskilled player in L4D, but in TF2 it doesn't bother me in the slightest.
Edited, Apr 30th 2009 11:33pm by Allegory