I have both cars....
I built the V1R first. The instructions can be quite confusing at times. The V1R is an awesome car....well balanced & well thought off. The battery, fuel tank, and steering servo, is right smack in the middle of the car. V1R comes with a radio compartment which I thought was pretty clever. I installed a Mugen MT12 RE & only have about 5 tanks on this car, and I could already see that it has lots of pottential. In particular the steering is great. Since I am only trying to break in the engine, I installed my old and worn out HPI tires. I was surprized that the V1R, made it seem like I was using high traction compounds.
Since I dont have the RR version. I ordered Kawahara Racing front and rear stabilizer bars, one way front diff, and a solid rear axle. (I would have gotten the RR if the store had it)
Otherwise it is a great car right out of the box.
I am currently putting the Serpent Impulse Pro together.
The instructions are great and well laid out. The parts bags are very well packaged in sequence. The main chassis seems to be softer than that of the V1R but it is also much lighter. The bearings are of very high quality. One negative thing about putting this kit together is that the threads on the lower suspension arms are quite tricky. You have to make sure that you screw the aluminum plugs properly otherwise you will destroy the threads.
I have only gone as far as assembling the rear transmission and suspension, and the front transmission. My fingers are all sore. The parts come together very tight.
If you get the Pro version it comes with front one-way diff, carbon fiber radio plate, front and rear stabilizer bars, wider rear foam tires, and an aluminum rear exhaust bracket.
Since the impulse pro is'nt finnished yet, I cant tell you how it handles. I'll post my opinions when I have the car done.