Both are great rides! Our favorites at DLR. You'll spend more time in Cars Land as the area is much larger than just one ride (RSR), but I highly suggest riding both.
Yes, GoG is like ToT in that you go up and down. But the experience is completely different, and I must say better. Music and video play on the ride now. There are 6 different sequences, unlike DCA ToT only having 1.
RSR is such a cool ride. Part dark ride, ending with a race that has speed like Test Track (not as fast), but you get to race another car. It's fun! You can have 2 variations inside the ride -- get new tires, or get a new paint job before you race. Both neat in their own right.
My theory currently is since GoG is new, head there first. If staying onsite absolutely utilize EMH. Ride GOG, pull FP for GoG, ride single rider RSR, pull FP for RSR when you can get a new one. You may not get to pull FP for both depending on how busy park is. Last month, GoG FP's ran out around 11am, RSR ran out around 12:45pm.