In reply to diggers: I've used various helmets over the years - Petzl Ecrins Rock, Petzl Meteor and now one of the newer style DMM ones. The issue certainly isn't as cut and dried as Tom or others makes out. There are good reasons for choosing any of the three main construction styles.
The Ecrin Roc is subperb in main ways - easily adjustable with hats/balaclavas, about as indestructable as helmets come, and pretty comfy even in warmer conditions. However it's very heavy compared to every other options. If you are seriously going to use and abuse a helmet (especially in winter) and durability is a high priority, it's the one to choose.
The Meteor is completely superb in every repsect other than durability. Unfortauntely I got less four years out of mine, admittedly not being at all careful with it. However, if you are occasionally reluctant to wear a helmet, ultra light is the way to go. If you buy one (or similar), there is a good chance you will be more likely to wear it on marginal occasions. It's cliched but a helmet you don't wear is useless.
The new DMM one is similar to the Elios - hard outer shell plus polystyrene inside. It's extremely good and once I've put it one I generally forget I'm wearing it - the sign of a good helmet.
For some reason my helmets get a very 'hard ride' and soon look worse for wear - in that regard the Ecrin Roc and older style helmets excel. The modern 'Elios style' still hold up well and are certainly less tiring to wear for extended periods - I wore my DMM one for 36 days in a row last summer with no issues. I was glad of it recently as it saved me a bruise or two when I took an upsidedown fall from Vulcan, landing flat on my back against the cliff face. Unlike the ultra-light ones I'm not too concerned about it being damaged in the process of that fall.
Despite being a 'regular' helmet wearer, recently there have been several occasions where I haven't worn a helmet where perhaps I should have done. That included today belaying at Cheddar where my leader pulled off some lose holds; a not unknown event in the Gorge. I can't say that if I still had my Meteor, I would have worn it, but this thread has made me consider it and I might well have.
You've probably more than enough info now to think about, however ultimately it comes down to a personal trade-off - if someone else was paying I'd have a Meteor III or similar...
HTH
PS Only other thing to consider is the apart for the Edelrid Ultralight, the Elios is probably the most unflattering to wear helemt on the market currently.