I own 3 E4FS cars and I can tell you that this design is fantastic. These cars may not be well known but they are quite good and different. There's a great thread for the E4 that should answer many questions for you. Here's a link.
Team Magic E4 Thread
That being said, I would be remiss if i didn't say that I agree with getting a car that has good support locally. Here in the US, we have Wolf Hobbies. A simple phone call and my needs are met. That may not be the case for you so just be aware of it.
The JR is identical in most ways to the other versions of the car. One thing of note is that the JR is plastic and can be broken in hard accidents. This is usually confined to the front of the car. Search in that link I supplied.
This chassis handles great. You WILL be pleasently surprised.
One question though....Why the RTR version ?? It's nice but the electronics and motor are all but useless in most classes of racing. The kit version of this car is the E4JS. Same chassis just no electronics.