They are quaint and homy and you really feel more in touch with your fellow gamer. It's more a sense of community and frienship than the sometimes distant feeling larger LAN's can have. It's all free play and we can usually get everyone there into the same game and that makes for some really awesome gaming.
All-in-all, the bounce to the ounce is much higher at a smaller lan. Like billabond said, you just have to be there to experience it.