Well, I was expecting a more environmental-friendly type of traction since in recent years JR experimented a lot with alternative energy sources and energy saving. After hybrid and battery experiments, recent orders for new multiple units for unelectrified lines are also of the traditional DMU kind again. This was also the case with the hybrid HD300, with them now ordering a series sort-of based off the experimental loco without the environmental-friendly stuff. It seems like things aren't progressing as much as they would've liked, or diesel is still cheaper than the alternatives.
Diesel electric over hydraulic is obviously a given at this point.
The HD300's are still in series production at a low rate and I think will be tasked with shunting duties only given their top speed is only 45km/h but they can be towed at 110km/h when being deployed to other depots. The main benefit with the HD300 is their low emissions which helps when working in yards near populated areas, especially when you consider the exhaust fumes generated by diesel locomotives from frequent acceleration and deceleration when employed on shunting duties. I suspect that cost as well as overall versatility is the reason why the DD200's are being introduced as the HD300's would more than likely cost more to build compared to a standard diesel electric locomotive, not too mention higher operating speed, tractive effort and range would all come into play with the desicion.