I was on WW from 1999-2003, and in between, briefly on Atkins for 2 months.
I am mostly vegetarian, except for the rare seafood, so when I went on Atkins, I DID lose weight quickly (9 pounds my first week, and 3 every week thereafter)... but my kidneys were killing me! Of course I wasn't used to so much protein. Ultimately, I couldn't deal with preparing meat to eat, and the clean-up. I got grossed out
Plus I would have killed for a glass of orange juice, and I became very constipated. I found it creepy to have to take fiber supplements just so I could go to the bathroom! The novelty of eating bacon and cheddar cheese as a snack wears off quickly I found. However, I must say I did have a lot of energy on this diet, and I wasn't hungry.
On WW, I lost 52 pounds by learning to eat correct portions, eat the ol' 5 servings a day of fruits and vegetables, and drink lots of water, AND exercise 30 minutes a day. I did this by going to weekly meetings religiously, and getting on the scale no matter how I felt I did. In the end, I was reassured that my body was an "honest machine" in the sense it just did what I caused it to do. If I ate too much, I gained. If I stayed on plan, I lost. Simple!
My energy level on WW is average I think. The first 2 weeks are an adjustment, getting your stomach used to smaller portions. I occasionally get hungry on WW, but to me, this is not the end of the world. Healthy snacks being handy help a lot! I think the kiss of death on WW is making the mistake of starving yourself for part of the day, then becoming so ravenous you devour anything in sight, Points Schmoints!
I personally like WW better. Unfortunately, I fell off WW in the middle of a stressful relationship, and went back to my old ways of pigging out to distract myself from my emotions... And gained 43 pounds back.
But I'm back!

I'm DETERMINED to lose 69 pounds, to go from 200 to 131. I've been on WW at home since this Sunday morning, and already lost 3.5 pounds from my 200 pounds weigh-in on Saturday. Of course, this is probably just waste and water, but it's good to see a drop!
I'm going to clean up my house and then go out for a 30-minute walk around the neighborhood since the YMCA up the street is closed for Labor Day.
Good luck to you, whichever diet you choose!
Sarah