I like to use Oster clippers because they seem to get through tighter curly hair. I have an Andis and do not like it at all, it does not seem to do a good job like the Oster does.
I would recommend going with the Andis. I have an Oster A5, and it lacks in power/ability to get thru thick coats. I recently got some new clippers (a Laube) and wow, what a difference. A lot of groomers seem to prefer the Andis over the Oster as well. Here are a few links where they discuss this:
Oh and if you're going to buy snap-on combs for your clipper, consider getting the stainless steel combs (made by Wahl) instead of the plastic ones. They seem to work much better on poodley type coats. :)