I have the Mugen, and its quite durable for the beating I have put it through. I would say the conversion needs a tad more to it if you want to use the kyosho 46T spur gear. You will need a kyosho or similar center diff. Or you can use the MSR part that mates with the ofna 51T spur.
I would say so far, the cleanest looking conversion is the losi 8ight as you still retrain your receiver box.
A local buddy has a Losi 8ight he wants to sell, so that is a prospect at this time. I have noticed that the 8ight sets up very well brushless. My only hesitation is that I've read some reviews that it is not quite as competitive as some other buggies. Of course that might be splitting hairs?
The Mugen is bulletproof, the parts is all in stock at A Main Hobbies, and i don't know why Cain spoke about the Kyosho 46T spur gear You'll never have need it, just keep the stock Mugen center diff, and go to RCM website for the Mugen motor mount.