I've come to the conclusion that it really just depends on the person based on their own metabolic situations. What works for one, may not work for another.
2012 was my year of experimentation ... I embraced high-fat Primal with gusto and didn't track what I was eating. I cut carbs, I tried IF. I gained 40lbs* back over the entire year after having lost 60 -- very disappointing when I stepped on the scale earlier last month. I also was not going to the gym, but I had maintained where I was at for over 6 months without it prior to switching to Primal.
*I only went up one pants size, or generous stretchy Express brand pants size, so while it did occur to me early on that I was gaining, I didn't realize quite how drastically. No, it wasn't muscle.
Now, I know what works, for me. I believe in cutting calories, however not going under BMR. I had mine tested and it's somewhere in the 1500s, so I try to eat 1700-1900, depending on activity. I'm back in the gym, lifting heavy and doing some cardio, and the weight is finally coming down again. I no longer cut carbs, however I do watch my fat because I'd rather it come from my own stores. Ketosis and 80% fat did not keep me satiated while trying to stay under 1600.
That doesn't mean I'm completely back to low-fat CW: I make sure the fat products I do get are grass-fed, and I still eat the whole [pasture raised] egg! I stay away from grains because they give me gas, but I will have pizza or a pastry if special occasion calls for it. I might be more "quality whole foods" or PHD than Primal now, but it works for me.
Here's to 2013