Well, which do you prefer and why?

Both

big powerful expensive flood on the bars with some long distance penetration and a cheap torch with a hot spot on the helmet for illuminating where I'm looking, around corners etc.

Both, Ayup mountain bike kit.

Bars creates more shadow and helps with depth perception. Head mounted allows you to see around corners.

Both here too but if I had to choose only one then it would be helmet mounted

It's mostly down to personal preference. I've always had a head torch, and when I tried a bar light instead I found it awful. Another club member found the exact reverse. Now I run a Hope 4 on the bars, which I admit gives a clearer view of the terrain, and a less power helmet light to see round corners etc. My helmet light died last night, leaving me very disorientated :-(

Both is good, I have a nightmare on the bars as a backup and a L&M Arc as a helmet mount light. If I could only choose one place for the light it would be helmet mount as its much better for technical stuff and tight corners

helmet are fine unless it's either raining or misty in which case you can't see a thing.

bar first, then helmet if you have to chose, both if you don't.

Only use a Lumicycle HID on my noggin. IMHO helmet light is essential to see into corners if you are doing trails that are the least bit bendy.

Up until a few weeks ago rode with my light on the bars but have recently bought a new lid that had a nice flat top so thought that I would try helmet mounting my light and I find it much better. The lights where you look makes sense really.
The disadvantage is that i keep blinding the people I ride with but i'm sure they'll get used to it.

Thanks for the opinions. I cant afford 2 lights and have used helmet mount up to now. I do find that even fine rain appears to be a blizzard which is really distracting. Im worried that bar mount might be less practical in case of mechanicals as I sometimes end up riding on my tod.

Some of the DX lights are peanuts – admittedly you have to buy batteries ($12) and a charger ($10) so it does stack up, but I think I dropped #25 on a torch last winter that goes on me 'ead and works a treat. As said above, you don't need a fantastic light on your lid if the bar mounted one is up to scratch.

Lid defo…light goes where you are looking obviously…handy for punctures etc, plus bar mounted is hopeless for steep dropoffs…agree it's dodgy in drizzle but still best compromise I reckon.

BOTH :)

Im worried that bar mount might be less practical in case of mechanicals

I use a Tikka mini LED headtorch for sorting punctures/mechanicals and emergency backup. Main lights are on the bars.

Both.
Though if I'd have to settle for one, bars when it's dry or misty, helmet any other time.

bars or both.

Bars.

IMHO helmet light is essential to see into corners if you are doing trails that are the least bit bendy.

Never really understood this argument,I ride in the Chilts, and the trials are wooded and twisty. I tend to turn the handlebars to where I'm going, unsurprisingly, and the lights at a much more useful height and throw when it's lower down.

Tried riding with a helmet mounted one last night, and couldn't get on with it at all, Found I had really distracting black blobs under my eyes, and kept unconsciously lifting my head to try to get rid of them…Well weird.

Both. If I had to chose bars or helmet then it depends what the light is, if it's a super bright floody light then bars, if it's something like a Fenix torch then helmet.

Helmet mounted for seeing around bends is very useful, you can't rely on just turning the bars for tight corners (unless you're riding super slow or have very powerful lights giving out enough sideways flood to light around the corner anyway).