I don't know about 6 or 6.3, but after a month of using the original Note at 5.3, I was thinking at the time the Note 2 should be 5.8. I thought back then that 5.8 would be the perfect size for me.
After Sammy released the Note 2 at 5.5, I originally thought it was too small (imagine that), and not much of difference over the original; I was wrong. I really like the 5.5 display, and this size works very nice for my use.
That being said, in my humble opinion, there is no size that TOO big. Only the market and consumer demand can determine when the size is too big. As long as people want a particular size, are willing to pay their money for it, and OEM's are not losing money, then they will build them to meet demand. I try to refrain from suggesting what I might like, or not like, is somehow the standard by which others should like, or not like, a product or service.
Hey, if people are willing to buy it, then it's not too big.