Ok, now i am looking for a good helmet -- and are any better than others? or is it just what feels good on your head?

Also what are the pros and cons of the full head helmets like the motocross and BMX people use?

Any helmet you buy is going to offer adequate crash protection. Government regulations ensure that.

Differences are going to be mostly about fit, weight and ventilation.

Shape and sizes vary from brand to brand and from model to model. Adjustment methods vary. You'll just want to try helmets on to steer clear of those that don't fit or feel right.

More expensive helmets typically weigh less than cheaper ones.

More expensive helmets typically have more/bigger vents than cheaper ones. This improves air circulation to keep you cooler.

Other than those differences, you'll sometimes see various bells and whistles that may or may not mean anything to you: slots for sunglasses, insect netting, vertical adjustment, removable visors, etc.

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.

i am probably going to use this helmet for most all my riding...i don't care if it is hotter than others.