I run the MBX5R so can only give you my experience of this buggy.
Pros
easy driving durable car which lasts, sets up fairly easy and is very tuneable, the diffs on this car really are bulletproof im the only person at my track to shim the diffs loose and not strip the diff, the package is really top notch every part of the car is high spec what isnt ally is carbon, you get a good handful of rear toe blocks with and without squat built in a choice of front blocks to change kickup of the front arms plus many other items standard.
Cons
the MBX6 is just around the corner
, some people will say price but look at whats in there, not as light as the 8 and RC8.
just my thoughts on the mugen
as for what to buy ?? does your track have a onsite shop if so buy what they have stocked in spares it may be the difference on race day, if you dont it doesnt really matter although it is beneficial to be able to ask other people running the same chassis for help these few things aside the choice is yours you spend your money and take your chances
