I would definatly go with the small size, as far as the power goes it depends on what kind of terrain your hunting. If your hunting were it is wide open and flat you would probably want to go with a higher power. If your hunting were there are hills and trees there is no reason to go over powered. Here is a site that might help you to understand better what type of power you want. (
www.stinggroup.addr.com) This is for scopes but it can also be helpfull in binoculars.
Striper Phil I have hunted both ways. I sit still now because of health issues. If a man/woman desides to hunt on the move they can be successfull as long as they know what they are doing. It has alot to do with knowing what to watch for, knowing wich way the wind is blowing, learning to walk and be quiet, Learning to take a couple of steps then crouch down and wait for awhile before moving on, etc... I do agree however that sitting still is easier and for most people it is more effective. just my 1/2 a cent worth