My son got me a 3S Big Rock for Christmas, and we have just gotten around to unboxing it and taking it out for its first rip around the yard. The 3S Big Rock is an amazing RC! It is fast and quite stable and yet it has good ground clearance to soak up the bumps. We do a quick comparison to the 3S Granite which is it's shorter wheelbase brother. The Granite is also a ton of fun but a bit more unstable due to its shorter wheelbase. These 3S Arrma monster trucks are remarkably fast and durable.
Out of the box, the Big Rock was slipping as you will see in the video, but it healed itself. The steering is a bit slow, even compared to the Granite, so we don't know what that is all about. Maybe it needs a trip to the hobby shop to get an expert opinion. It didn't change that it is a ton of fun and remarkably stable even at high speeds.
I don't have enough drive time with the Big Rock to give a recommendation over the Granite, but I can say for sure that these two 3S Arrma vehicles are super fun and you will not be disappointed with either one.