So far the Kyosho plastic looks similar to Mugen (arms and hubs). What I am surprised about is that you get a full set of arms with your purchase and they are cheaper to buy. For the MTX-3 arms you were looking at 15.00 (upper then lower) when the Kyosho RRR comes with upper and lower for $7.00. The packaging could be different with the MTX-4.
Don't worry I'll let you know how durable the RRR is because I'm every which way but the 'line' lol.