Of the three, I have only tried Medifast, so cannot give you subjective advice. I am a foodie and I was concerned about eating artificial food, but I have to say I loved it. I discovered I can only efficiently lose weight on a low carb diet and packaged foods took the hassle of counting calories and carbs out of it. I added spices, a few veggies, and fresh herbs to everything and generally cooked the foods rather than microwave them. Medifast puts you in mild ketosis. Because of that I was not hungry and I have the impression that fat loss is encouraged. I did exercise for a while before going on this diet,so I had some muscles and those were preserved during the diet.
As to starvation mode, I am not sure that really exists. If you are overweight/obese, your body carries plenty of fat, which can be used as a fuel. What I noticed myself now on low carb and very low carb diets is that thyroid hormone levels are reduced when starved for carbs. In people with normal thyroid function, this may not be a problem. But if you are subclinical, you should monitor carefully. Once thyroid hormones go down sufficiently, your metabolism goes into the cellar. If these diets are done for a couple of months only, this should not be a problem. Medifast is only mildly ketogenic, which preserves thyroid function much better. I had to recently stop another very low carb diet that only provided half the carb than Medifast does because of thyroid problems.
As to regaining, I think it is a personal issue. Some people will feel deprived on these diets and once at goal, they just fall back into old habits. Phasing off should help as was already recommended above. I think Medifast does a pretty good job in this regard. I did not phase off, but I keep track of what I eat. 1500 calories are enough to loose at a very slow rate. My maintenance is around 1800 (age factor is terrible). I exercise, too. Once you stop with these limiting diets, you have to find the range of calories that keep your weight stable and in most cases, this range will be much lower than you'd like. I don't like sweets and desserts and don't eat fast food or go out regularly. This makes it pretty easy for me to maintain. But you will have to remain alert forever. For me, weight loss is mostly a battle that happens in the head.
You can purchase entire lots of food on Ebay to save money. Medifast really kickstarted my weight loss and was a complete eye opener regarding the role of carbs in my previous weight gain. It was worth every dollar. I actually just re-started it to tackle the next 10-20 lbs.