I am a resident engineer on a site that has ran the doosan D20SC-5. These little trucks racked up 10k plus hours in under 3 years and I can honestly say as long as servicing reflects useage these trucks are bomb proof! Had one diff (warranty repair) and one water pump. No other major repairs at all in three years. Running the kubota engine with a tyre saver device protecting drivetrain.
My site recently changed to the B20x-5. Still an unknown quantity to my but I've known of plenty of motor faults requiring a remove/replace.
Premium brands fill their machines with superfluous additions that neither aid the driver and inflates repair costs. I work on all the large brands and can vouch for that myself. Doosan diesel is a safe bet for a simple,quality machine

Edit: we in the UK get genuine parts next day for Doosan.