Swiss Ball : Which one should I buy???

[Buena Girl]

I ordered this book that njc suggested in one of the Daily Workout Threads:
PowerSculpt: The Women''s Body Sculpting & Weight Training Workout Using the Exercise Ball
by Paul Frediani

My question is what ball should I buy

There are so many brands. And different sizes. They also have different options for the ball like stands for the ball so that it doesn''t move, and pumps to blow the ball up.

I would love to get opinions from everyone who has tried the swiss exercise ball.

THANKS!!!