I will take a stab at this but my perspective is similar to yours as I just bought my first 1/8 scale.
Between the Hyper 7 and the Comp buggy, the Hyper 7 probably will be a better race platform. The Jammin however would be tops over the those two and would be newer as Ofna does have a Hyper 8 in the works but no release date as of yet.
As for differences, I think it has to do with suspension configuration among other things. Others will be able to better explain.
Now, when I looked into what was available for buggies, I checked up on Ofna first as I figure for my first vehicle, I didn't need some really high end buggy to start with. I didn't mind RTR as I was going to tear it down anyway and rebuild. Main thing would be a good manual for that part.
I wanted something that was a newer release so it had the potential to have alot of the hot features that the current set of buggies have if you know what I mean. When looking around, my choices came down to an Ofna Jammin RTR or the new CEN Matrix RTR buggy. Looking at the features you get with each vehicle out of the box and gear, and reading up on reviews and how they are doing at races, I decided to give the CEN Buggy a try as I figured for the money, I got better electronics, better servos, and the buggy was being raced by very top drivers and was having great success.
I have it now, and I am going to do a full teardown and rebuild (CENs manual is VERY nice too) and I am pretty impressed so far with it. Everything feels beefy on the buggy, and I like the little things it has on it as well.
CEN also has an ARR version of the Matrix that has no engine, etc so you can get a race legal one (I am looking at the OS RG to start with ). They also have a Pro kit coming out too.
I would say take a read on both the Jammin and the CEN Matrix, and see what the reviews state and what drivers who have the vehicles are saying and make a decision from there. This is not to knock other vehicles, these are just the two that I can down to and you may find others you like better.
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