Preference for helmets is personal , when racing motorbikes off road i always went open face i hated the heat build up, inferior downward vision and reduction of hearing, Troy Lee do make an open face helmet for MTB riding although there is little demand for them as for DH racing they cannot be used, I have seen some free riders wearing them, many who ride all mountain stylee rigs also ride DH events will have to have full face helmets which is why you see so many wearing them.
Although MX helmets may be stronger cheaper, because of the forces when decking a motorbike they have to be a lot stronger to deal with abrasion and impact, this is not as critical with mtb helmets so they can make helmets with better venting keeping you cooler, they tend to be less bulky and more trimmed which means they do not feel quite as much the dumbell strapped to your head a mx fullface does. Troy Lee and The are popular, I have a Remedy which is good well vented and I believe is the std issue helmet at most Whistler Bike Hire Centres (which is why many riders over there choose not to buy them). Specialized are popular I have always been surprised at how good the pricepoint is for Bell Helmets given their Motorbike Helmets used to be about the most expensive you could get. The Bell designs were not that stylish and you rarely see them but with the Athertons and CG wearing them they should not be ignored. I do however agree with Curly68 about helmet locks D rings are better , buckles are ok but you have to make double sure they are clipped up before you pedal off.
Goggles there are 2 problems with ski goggles. Traditionally they are made to wear on a bare head, because of the way the strap connects to the frame if you wore them with a helmet they would not rest on the face but would sit stretched across the opening of the helmet creating all kinds of comfort, vision, and misting problems. If you have a pair of ski goggles built for a helmet, the lenses are usually high grade for sun management, only have to contend with snow flakes and drops of water hitting them. MX goggles have to deal with roost from wheels which contains mud rock and grit which can both damage the lens and your face. A mx goggle with a few pairs of clear lenses is the better option unless you can afford to toss away scratched ski lenses like tissue paper.
Would I wear an MX helmet on a MTB .. no way, without spending a fortune, they are hot and heavy and beside Elbry Sandland wears one which is sufficient of an un-endorsement for me
Good range of colours and sizes 
