Lonecowboy,
I agree that a skilled driver with a powershift (gst and equivalent) can equal or best a novice on an HST tractor. But a novice on an HST tractor can best a moderately skilled person on a powershift. Equally skilled operators on HST equiped tractors nearly always are more productive. I don't know of many situations where a crash box gear trans can even be thought of as being in the same ball park as an HST. (or powershift for that matter.)
Also (hate to pop your bubble), but HST transmissions have the same or fewer parts than a gear trans or powershift and have greater overall reliability. Cost to repair is dominated by labor for both and most mfg only want the service departments to swap out for rebuilt transmissions and those cost about the same (high) price.
I didn't know there had been any productivity measurements one way or another. It is a matter of opion. I don't recall seeing any large ag tractors with HST, wonder why that is?
I have never seen anyone on theis board say, "Gee, I wish I had gottne a smaller tracator." Get one of the larger tractors you have mentioned, the John Deere 5105 or Kubota
M5040 or the New Holland. You won't be sorry....