This isn't quite true. Tight, but aggressive wins more consistently, but if you are a good reader of opponents or can create good table image it pays to be a lot looser and take advantage of your skills. Still players should try this first, then branch out. Look at the big winners in tournament poker, few of them are Dan Harrington types. I guess the takeaway is if you want to be a good winning player, tight-aggressive is a good choice. If you want to be world class you probably have to play a more imaginative style.