depends on the size of the tv and how close you sit.

most won't notice a difference but will tell you they can.

audio is the same

Actually, ppl. always think of 480, 720, 1080 etc...but in actual got many things that effect quality of the image like Bitrates and Reframes and of course the hardware itself
Sometimes, even 720p can give a better picture than a grainy 1080p version... even between 1080p and another 1080p release version there will be difference.
Take for example TF2...got so many 1080p releases...from 11Gb to  45Gb..

The difference in image quality differs individually. Some ppl want the best..hence go for BDisc..and some are just movie lovers who think 720p is more than enough.