If you can only afford one light, buy the helmet mount one. If you looking at the NR HID Enduro, it only comes with the helmet mount. You can buy the bar mount kit for $30. When you are making turns you always look left or right and the light points to where you looking at going. If is on the handle bar, you will not be able to see into the turns.
The LightNMotions do have a slightly white/bluish light then the NR's. The battery weights less too. NR's last as long as the LNM's and charge in about the same time. Just slightly heavier but $100+ less.