4) People ignore the advantages such as native 1080p videos, better cooling, bigger screen, extra USB port and overall prestige.
It also has an ExpressCard/34 slot, useful if you want to use eSATA external drives, for example, as could then make use of an eSATA ExpressCard/34
5) People make the 15 out to be the sweet spot because they think one is too big, one is too small, one is juuust right in the middle. But thats not the case. Anything less than the 17 is a concession usually due to money and we don't live in a fairytale world.
I'd still go for the 15" model personally, if buying again today, and not just because of the money, but everyone has different requirements