About your last question, well I prefer full face helmets for anything thats not XC (and maybe trials but thats debatable), XC style helmets are much more preferable for XC as they are cooler, offer better visibility and are less cumbersome, if you want a kind of do it all helm a bucket or skate style with or without jaw protection helmet is an option.

And yeah peek the geek has the rest, you want to try every helmet personally and see which offers most comfort and which one suits your needs the most.