I have several Minox instruments (scope, binos, monocular, and spotter) and they are all leaders in their price range.
With optics in general you get to level (95% or so) where spending two or three times as much is required to see a small improvement.
I replaced a Vortex Razor HD 20-60x85 with a Zeiss Diascope 20-75x85 FL T and the difference was very small, a tiny bit of brightness advantage to the Zeiss, and of course another 15x.
If I didn't have optics ADD I'd have just returned the Zeiss.
I doubt you will see much if any improvement over the MD62 in a Viper spotter.