I handled a Samsung GALAXY Mega 6.3 a few weeks back. I was put off by the size. It was way too large. Mega may mean big, but that 6.3" size was way too big. I wanted it to be a phone like the Samsung GALAXY Note 2. A phone I can comfortably slip into my jeans pocket. I just could not lug it around every day as it was too large.
I have a GALAXY MEGA 5.8 on my desk now and I do not have a problem with that size.