I've been driving tractors for over forty five years and selling them for over thirty.
You need about 5 extra horsepower to over come the flexibility of speeds on pto work on a thirty horsepower tractor between a hydro and gear drive to get the same work done.
You will get better fuel economy with a gear drive over the hydro can't top that..
My L4350 w/gear drive seems to be better on fuel than my B7800 w/HST and it is a much larger tractor!
Hydro is the number one seller.
After using my B7800 I can see why, back and forth is effortless and a time saver with loader and other work.
There are places that a gear drive can be a plus but even new farm tractors are getting more flexible with shuttles at a minimum and of coarse the latest is CVT which is vary simular to a hydro in application. This type system came from Europe even though they perfer gear drive cars!!!!