I like ww on-line because it is easy and doesn't take time away from other things I want to do, like spend time with my son. I am a working mom, and my husband is a SAHD, so time with my son is important to me. I don't really need the meeting-aspect of ww to keep me on track. I know that if I fudge and fib on the on-line accounting of my weigh-ins, the only one who hurts is myself.
Plus, I like the community here for advice and discussion. Everyone is very knowledgable and friendly/supportive.