Unless you have a consistent need for long range viewing, 10-power binoculars are unnecessary and could be problematic for you. They have to be held extremely rigid or what you are trying to view will be dancing; usually have a smaller " field of view" (which (FOV) is a plus to reduce head movement), have a smaller depth of field (cannot focus well on objects that are at a close range), and, depending on the quality, the view is usually darker then it is through a 7 or 8 power.

I have used binoculars for hunting and professionally and I have personally found that 7 and 8-power x 35MM, wide angle, with FULL COATED LENS and adjustable focus to be the best all around bino' s for quick and steady use. In the timber, I like my 7X15X35MM with " quick zoom."

If you have a need for long-range use, or need to count the hairs on a deer….that is not too close, then 10-power might be best for you. Otherwise, you may be committing " overkill" and may find you have spent a lot of money for something that will not perform as you expected or desired.

As for " roof vs. porro" prism; again, what is your need to justify the cost…especially cost for repair? Both my binos are " porro" and I can see the deer just fine. My 7X15X35MM are older " Sears" model that I have banged and drug through the dirt, rain, and snow for several years. I can still cleary see the distance and object I need to see for the brief intervals and time I would be glassing while deer hunting.

In the end, it is a matter of personal choice and the right to spend one' s money as he or she wishes. However, in this case performance will rule in the end.

http://www.backyardhabitats.net/Optics%20Info.HTM