To be completely honest I haven't build a kyosho ball diff in ages... those I've done were either AE (B4 and B4.1, B44.1) or Xray (touring car). The Xray is fantastic and requires few rebuilts, but the AE offroad stuff does require regular maintenance, especially on the 4wd cars - 2wd is better but still I like to rebuild after every race. This isn't much but I have less and less time for RC as the years pass by and the kids suck my capacity. If you tell me the RB5/6 ball diff is top-notch and will stand the abuse better than the others, then I might listen
I started building the car yesterday evening, didn't go far though, just the start of the front end... the quality is just stunning despite one of the steering post hex being a tiny tiny bit too large in the bulkhead. The way every part fits just "tight enough but free, still" is unbelieveable... This will be a very, very nice build that's well worth the money (even accounting for the value I lost running a dex210 - with a crappy gear diff I must say - for half a day only).
I love it already
Paul