If you need to use dichlor in your spa (... because you would NEVER use dichlor in your pool, right??? :ncool then the brand is really irrelevant. You simply want to make sure that you are getting pure dichlor without any additives in it. Some of the combo products (like the Clorox line of pool and spa chemicals) have dichlor in them but it's usually only about 50% or so. The rest is made up of baking soda and borates to help counteract the acidity and, heaven forbid!, copper sulfate to act as an algaecide.
Stick with whatever is the cheapest and purest stuff you can find.