Definitely low carb for me. Before I finally decided to try it, I had always just limited my calories. But I was ALWAYS hungry and I ALWAYS gained the weight back extremely fast.
Whether I'm dieting or not, I always work out at least 5 days a week. That will always help. Low carb doesn't get the weight off as fast, but it's very easy to stay with the diet and I get to eat until I'm full!