I've never heard of BoneSmart Pilates. I had a quick look, and it says it "addresses correct and healthy body alignment and offers a safe method for improving strength, flexibility and balance that is useful for anyone interested in aging with power and grace." This could describe most forms of Pilates. It seems like it is classical Pilates with some modifications to make it osteoporosis friendly. Stott and Windsor take the classical Pilates and put their own spin on it. I've done quite a few Stott Pilates workouts and a couple of Windsor Pilates and I prefer the Stott ones. Both styles use the main classical moves especially in the beginner level workouts. I would say that Stott tends to be more athletic, and sports person focused. Personally, I find the Windsor ones a bit boring.
Others I would recommend are Dez Fit and April Plank. Both have free workouts on YouTube. I mostly do their reformer workouts, but they have some mat workouts on their sites. They also use props like a mini ball and resistance bands. They tend to be a bit more athletic.