I use the 600 on my helmet and an aldi ‘1200’ but probably really 900-1000 on my bars.
However when I crashed the other day I knocked out the wires from the aldi light and had to make it down some fairly technical wooded singletrack in the pitch black with just the 600. It was no problem but i wouldn’t have wanted to do any fast flowing stuff – 600xl is very much a spot
However the 600 is a fantastic light with excellent build quality and mine came in the loaded pack with 2 batts for 50 quid or so
Paired with the aldi (now fixed and improved) which cost £20 and an upgraded battery from magic shine £35 I have a brilliant set up with a spare batt for each light for approx £100
as for security, the bar mount for the 600 is very good but the helmet mount i found to be a bit flexible no matter how tight you do it up so I superglued it. No adjustment but rock solid!