Lots of people like both. Been hearing lots of good about max8 lately. And with hobbywing north American the customer service for hobbywing is much better than its been in the past. Im going for the max8 combo for my talion. Bit cheeper too. I just gotta save the scoots. A few members on here just got the max8 and They are more than happy. Hope this helps
I have a bunch of the Castle's and I love them. I know you can get new ones on Tower Hobbies and use their coupon codes to save a good chunk off the price.
I have a Kraton with the mamba monster x, and a senton with the max8. both esc's provide a HUGE upgrade over stock. at this point I can't see either one being "better" than the other. I would recommend getting whichever you can get for a better price, or whatever you feel more comfortable with. I know some people shy away from hobbywing because they are a "chinese knock off" I've had great luck with mine.
If you are going the castle route, I would recommend the mamba monster x over the mamba monster 2. simply due to the much more powerful bec.