It's true that traditionally gear drive is THE field tractor application. However, the eHydro design in theory negates that because you can also set the speed you want and regardless of load, the eHydro will keep the speed by varying flow to the transmission. The computer takes care of it for you unlike a standard hydro system. As long as the reliability is there over 20+ years the eHydro gives you the best of both worlds.
To me, the disadvantage of eHydro is that I might not be able to get parts 20 years later and it is a more complicated system. Gear is easy to work on, as is standard hydro. I don't know if it will matter in practice but there are lots of really great 20+ year old tractors going strong and hard parts are still available. I don't know if fried circuit boards will still be there...