I'm another with experience of both yoga and Pilates. I feel rather like I do about recumbents and uprights - both good but very different.
The yoga style I did was Vinyasa, which is a rather more aerobic style as the emphasis is on moving - flowing - between the postures rather than slowly rearranging yourself after long periods in one posture, which was my (short) experience with Hatha and Iyengar. I found it was good for overall suppleness, especially in my back, and it developed quite a bit of upper body strength too. As I'm not someone who has problems relaxing, I find all the meditation & breathing stuff a bit of a waste of time but I think this is very teacher-dependent.
The Pilates ('Body Control'- style) classes I attend are very different with much more emphaisis on core strength & posture. They don't do anything for general suppleness or strength of other muscles, although again this is a function of these particular classes and if you could get to classes using equipment, like a Reformer, it would be very different as it is a whole body conditioning scheme. Unfortunately, it seems that Pilates is mainly taught as a core stability activity, based on mat work and maybe resistance band work. Few studios outside the cities have invested in the full suite of equipment that could make it a real rival to yoga.
Consequently I go to a class a week of each and practice fairly religiously (but sans God
) at home to get the maximum benefit.
I suspect that Wii practice may be fun but not a substitute for getting hands on instruction from a good teacher for either yoga or Pilates. It's fair to say that both can create problems if done incorrectly so it's probably best to at least find out the right way first.