Technically brightness is how many nits the light output is, sure. But AMOLED screens have lower reflectivity than LCDs and hence are brighter for outdoor use, or under harsher lighting, etc. A 300-something nits AMOLED would be 'appear' brighter than a 400 nits LCD. Saturation is something else entirely.lol dude LCD screens are much brighter than AMOLED screens, its one of the advantages of LCDs. You are talking about saturation which has nothing to do with brightness.
And yes I agree with you on the PPI part, my 233 PPI non-pentile phone looks razr sharp to me people are just obsessed with the magical 300 number.