No argument on the Tekno, top quality right out of the box. Both of mine are 2-3 years old. Still tight. Haven't opened a diff aside from changing fluids. Can't say the same for my Arrma's. 6s need diffs almost yearly.
As far as electronics go, radio and servo are about the only downsides for Arrma IMO. Motor/esc are fine. Servo is about as good as any rtr. What chafe's my arse about Arrma is how quickly they develop slop at the suspension pivots. Might be the worst I've ever seen in 1/8 rc's. Even the 1/5 8s, sloppy right out of the box, and no way to fix it. It's just how they're made I guess, lose tolerances. Traxxas does better, especially in large scale 8s.