I don't think one style is more effective than the other. I think the effectiveness of any style is dependent upon the player and his understanding of the game and his opponents. For instance a loose player can take advantage of certain boards because he knows that a tight player wouldn't be calling raises with the kind of hand that would have connected with it. At the same time, because of the loose player's willingness to play a wider range, it's hard to know whether he connected with the board or not.
While LAG and TAG styles both have the aggressive part in common, it is my opinion that the loose players tend to be more aggressive. This is because the loose player could be holding anything. Sure he might be holding small cards that connect with raggedy flops. But then again, it's not like he's going to be throwing away premium
hands either. He's basically unpredictable, or at least very hard to predict. A good player will understand this and know how to take advantage of that style of play, when to be aggressive and when to let go, as opposed to LAGtards that don't seem to know the difference between looking strong and looking desperate.
Tight players are almost always going to outnumber the loose players. But by definition, they are also, as individuals, likely to play fewer hands than the loose players. But if they are smart, they too can take advantage of their images. For instance the tight player is more likely to have connected when face cards hit the board. The tight player can represent having connected with those face cards by betting out, or represent even more strength and confidence by taking advantage of the loose player's aggression with a check/raise. Not only can this effectively shut down a
bluff from a loose player, but it can also get them to lay down a weak pair if they believe that you've hit a bigger pair.
Don't be mistaken. There are a lot of loose players out there calling light in hopes of getting lucky and hitting the perfect flop for their hand or willing to call off half of their stack chasing draws. In fact, that's probably how the majority of loose players play. Most of them will lack the necessary aggression to be effective. At the same time, there are a lot of tight players that also lack aggression. They are willing to limp in with hands that they should probably be raising with. By not raising they allow more players into the pot, which then makes it hard to play aggressively after the flop. After all it's hard to feel confident when there are five players in the pot and you have to wonder if you're outkicked or if someone hit two pair or a set.
So I'll say it again. The effectiveness of each style is dependent on the player and their understanding of how to utilize the advantages of that style. Each has it's advantages, but I believe the key to each is aggression. Not out of control, chip spewing aggression, but as the say in boxing, effective aggressiveness. The stronger a player's overall understanding of the game, the better they'll be at taking advantage of whatever style they choose to utilize.