Assuming the same total power delivered, the high current solution will have greater fire risk and the higher voltage solution will have greater shock risk.
Both are very dangerous, but I'd agree the higher current solution (low voltage) is a lot less likely to kill you if something goes wrong, assuming you don't get stuck in a burning building.
When working with higher voltages, it's very important to ground the heat sink. If's not grounded, and the 400V wire comes out of a cob holder, and touches the heat sink, the light will turn off, and it will seem totally safe. The only problem is the heat sink is floating at 400VDC, and touching it could put up to 500mA through you (limit), easily enough to kill you. If the heat sink is properly grounded, the 400VDC wire touching the heat sink will instantly cause a short circuit, and trip the breaker, fuse, or short circuit protection.
I honestly don't feel safe using a 400VDC driver myself, so I did not want to recommend it in the materials list. If i'm not dead within a year, go for it!