42mm gets the hype because it's bigger (duh

) -- it's got a little more battery life (which was such a concern for many buyers), and bigger watches are the current trend.
The thing is, Apple's measurement, being lug-to-lug, is different from most other manufacturers who just measure the diameter across the case. My 42mm AW is about the same lug-to-lug as, or even a bit smaller than, my Rado, which is spec'd at 38mm diameter; and the AW is definitely smaller than my 43mm Citizen (which is as large as I want to wear anymore).
I would've gotten the 38mm myself, too, for my 175mm-ish wrist. I could say that larger is better for legibility, but since we can increase the font sizes, it shouldn't matter much. My wife suggested the larger size anyway.
Regarding missing the AW --
I don't think about how much I would miss my AW until I try wearing my other watches for a couple days in a row. Suddenly, all the little conveniences are gone -- I miss calls and texts, I have to grab my phone twice as often for piddly little things, etc. If I want to wear one of my regular watches, I have to plan ahead and be confident that nobody will need to reach me.