Prevention is not Cure
"Hi, I am suffering from pain in my lower back. It has been going on for some time now, about 6 weeks of so. Hot packs and heat rubs don't seem to be working as before. And it seems to be getting worse. I heard that Pilates and Tai Chi is great for preventing back pain, so I was thinking one of them. Which would you recommend? Thanks!" - Pauline Shi
Sorry to hear about your back but first things first - prevention is not cure. Prevention is great before your have your problem. When you have a problem, what you need is a cure, not prevention. If you are injured in a car accident, you don't try to heal your self by wearing a seat-belt in bed. Nor will drinking more milk help your bone fracture heal right.
So the first thing I would recommend is that you seek proper medical advice for your low back pain. Doing Pilates or any other form of exercises at this stage is not likely to help and may even aggravate it.
Once the pain is gone or properly managed, you can then look at either Pilates or Tai Chi to prevent the pain from coming back. As to which is better, both have a great foundation in core stability and strength. If done right, these exercises can go a long way in helping you strengthen the right muscles that's required to support your spine. Yoga is another exercise you might want to consider.
But do look for a reputable instructor, these muscles are located deep within your abdominal area and are hard to activate. More so, for people with a history of back pain. Good instructors will know if you are doing the exercises right.
Here are some past MCR articles that you might find useful.