Which one, Which one?

I think you have 2 very good choices there! I've not been to either, but I'd bet that you'll get more than your money's worth from either one.

I sugest that you take a mx school whit smaller groups. What i remeber these two does large groups.

Another option go to some of your local races and ask around. I would bet 1 or 2 of the A riders holds classes. This way you could see them ride and talk a bit with them before laying your money out. 1 or 2 riders with the instructor for a day will benefit you alot more then 30 students and 1 instructor no matter who is teaching.
When the classes get bigger the level taught tends to emphasize the median rider so the advanced and the beginner get a bit shortshifted