I have done both, Pilates and it is alot of stretching, I used to dance classical Ballet and a lot of Ballet Students use it to get a leaner longer look, It works but I have found that Power Yoga is great for strengthing your muscles and it makes you sweat as well as giving you the benefits of a lean non-bulky look.
Personally I felt that the Pilates was too low impact for me to loose the amount of weight that I have gained. So, Power Yoga is a better cardio and strengthing exercise for me. Pilates was good for stretching and flexibility.
Also remember everyone's body is different, your body may react to one better than the other depending on your goals.
I have tried Windsor Pilates and also the Power 90 program has some Power Yoga in it.
Current Goal: Loose 20 lbs by my birthday