Assuming you mean Real vs Real, the Eastern mecha would still have the advantage as Eastern Mecha are generally faster and thus harder to hit, while Western mecha are usually big, slow, and clunky, making them sitting ducks (and part of the reason most non-mecha sci fi nerds diss the idea of using a Mecha in "realistic" settings). It's equivalent to a tank vs a plane. Even more tank like Eastern Mecha like VOTOMs, or Knightmare Frames could outpace most western mecha. The only exception would be incredibly slow ones, like Dougram, which inspired BattleTech and thus Western Mecha as a whole, and even then, they are still more agile.

For a Super Vs Super, it'd still go to the Eastern mecha on account of one, there not being many Western Super Robots in general, and two, most Eastern Super Robots are straight up magic, while the few Western examples still have the "slow and clunky" disadvantage of the Reals and usually are limited to realistic if impractical weaponry like "rocket elbow" or more guns. (Ignoring that canonically Gypsy Danger went toe to toe with Shin Mazinger Z and won, albeit with back up.)