In Yamaha you are probably good either way. In TAG the Tacho was our favorite for a driver in the 175-180 range while the Dragon with a 135-140 pound driver was just awesome with a Rotax (or TAG). Despite what the frame designs look like, the Tacho drives an awful lot like an OTK kart.
Both great karts with fantastic workmanship in terms of frames and components.
(BTW – Have a sweet slightly used Tacho available right now with ALL of the goodies….)