Have done some yoga over the years but can't get my head around why I should aim to get into largely uncomfortable poses, and hold, eg the lotus position, where there is a likelihood of over-stretching knee ligaments. However, I am biased, as I am a Pilates instructor, and richardjohnson is quite right in his definition of Pilates. It is ideal for anyone at any stage of life, but dependent on a good instructor.
I recently re-located and attended 5 Pilates classes. Two were obviously Pilates, and they had trained through traditional Pilates schools: a longer more intensive (and expensive) training. The other three were totally and individually different, and they were all fitness instructors who had trained for two weekends with fitness training establishments. It was very apparent that they had spent insufficient time getting to grips with Pilates: one had abandoned all attempts at Pilates; another hadn't understood the basics, a little of which she tried to incorporate - and there are no Pilates police.
I emailed the ratifiers of the majority of fitness courses, which includes all the original established Pilates training establishments, and the response was that "no-one knows what Pilates really is." So I regret that that is why there is a huge discrepancy in the skill of the Pilates instructor.
Pilates underpins everything we do, and is about breaking down poor postural habits, replacing them with efficient movement patterns, so that we suffer less from injuries, aches, pains and wear-and-tear. It is an exercise system that adapts to your body, rather than being forced onto your body, as with other systems.
Pilates is a very good complementary exercise for golf, improving handicaps even for those who have back problems and are not highly skilled at Pilates practice. My DBH does it twice daily, and I do it daily, to manage the encroaching and painful osteoarthritis, for which Pilates is ideal.