I've used 6, 7, 8, and 10 power binoculars over the years. 10 power is useable, but really too much power. It is harder to hold steady, has a narrower field of view and is usually larger than 8's for a specific brand and model. 6x seems to be the best power, giving good resolution and a wide field of view in a small package.
I had a nice Nikon 8x ProStaff, but they were somehow left in the woods so I now have a Bushnell 8x Legend that is working very well for me. I had been looking for 6x, but there doesn't seem to be too many out there.