Kneeling Chairs & Sitting Balls

What are the relative merits and disadvantages of "traditional chairs," "kneeling chairs," and "sitting balls" to facilitate a healthy spinal position while seated at a desk for long periods of time (as so many of us must do)?

As well as any recommendations on how to choose a well-designed / constructed traditional chair, kneeling chair or sitting ball, depending on the approach one decides to take?

In regard to my own personal experience, I borrowed a kneeling chair from a co-worker for a couple of weeks, and found that it was much easier to maintain an anteverted (or at least neutral) pelvic position while using the chair.  I believe this improved my lumbar/sacral pain.  I found an advantage was that it was almost impossible to fall back unconsciously into a slouched (tucked) position.  However the overall chair height was not adjustable so it was not a perfect solution for my specific workstation.  I also found myself sliding forward and down a bit on the kneeling chair's cloth covering, as I sat for extended time periods.  This required me in turn to change the direction of my eyes relative to my computer screen, and change my cervical curve (by looking slightly upward, creating a bit of tension at the back of my neck, not an ideal position).

I have not used sitting balls, but I've heard some people recommend using them because they also facilitate a healthy pelvic position while also requiring a bit of positional awareness (probably a good thing) during extended seated sessions.

Finally I've heard it suggested by more than one bodyworker that the key is not so much what position one sits in (within healthy limits, of course) as it is to develop a regular habit of standing up and moving one's body on a frequent basis and then sitting back down in a different position (perhaps having more than one chair at one's disposal if possible).

Many thanks in advance for any useful information and ideas along these lines!

-Richard W.