I think the biggest difference is that the RTR has a moulded +8mm chassis, whilst the non-RTR has an aluminium plate+moulded sidepod chassis 8mm shorter than the new chassis tub. I think the +8mm chassis (and moulded tub) may (also) be featured on later version/2013 spec DEX210 (non-RTR).
Besides that, it doesn't have the two extra gears, one axle, two shims and two bearings included for the mid-motor conversion.
Also, the car has a gear diff, whereas the non-RTR has a ball diff.
From what I know, those are all the differences on the chassis really, which isn't too bad for an RTR - it seems to me they haven't cut back on the costs (and quality) of the regular DEX210 to make the RTR
