It depends on your goals and how many you have time to manage - LOL. I have one blogger for stamping, one typepad blog for business, starting another blogger blog for scapbooking, and then another one (Blogger) for a book. So you can have many blogger blogs setup under your one account, or you can setup blogs on many platforms. Blogger is free. Typepad is not. WordPress has free sites as well as paid services.
Have fun