Medifast/wonderslim dieter over here.
I'm just finishing a round of Medifast and have transitioned mostly to wonderslim. Medifast is more nutritious, easier to follow because the entire program is mapped and fine tuned for success, when you follow the program strictly. After about a week the food is tolerable.
Wonderslim on the other hand taste delicious. is cheaper but not as well fine tuned as Medifast. I suggested to a friend that she try Medifast first, be very strict and learn the program then begin to substitute Wonderslim or New lifestyle products when she feels confident.
I lost 19lbs in about a month using these products. But, I had been simply "low carbing" for 2 weeks prior to starting and was not losing even though I was in ketosis.