Most suitable brand for the roughest roads?

The more features you have the more that can go wrong. Still, it depends if you will slow down and have good shocks or not. I've taken mine over a lot of gravel roads and mountain fire roads without an issue over 10 years. Other people haven't been as lucky. I do slow down when I see the bigger bumps.

I can't say I'd pick one brand over another for just traveling rougher roads. There are advantages and disadvantages of each construction method. Slides are more complicated, but I wouldn't give up my slides.