The 8x42s feature a porro prism system which allows for greater depth perception and a wider field-of-view than the 8x 42s' roof prism system which allows for a slimmer form and greater durability. Otherwise, the two sets of binoculars sport the same basic features, including multi-coated optics and 100% water resistance.
The 8x42s' porro prism system refers to a front lens that is offset from the eyepiece (as opposed to lined up squarely with it as in a roof system), resulting in improved depth perception and field-of-view but less durability than roof binoculars. Their multi-coated optics provide the 8x42s with glare reduction and superior light transmission over uncoated lenses for an overall brighter image. Additionally, the 8x42s are 100% water resistant thanks to an O-ring seal and nitrogen purging, allowing for optimal performance in wet conditions.