My personality isn't really different between the two, but my attitude or frame of mind is. In blitz to play well I usually have to have a higher energy level and somewhat aggressive mindset. Which come to think of it might make sense due to the nature of blitz which involves quick calculation and checking tactics/forcing moves often.
In games over 15 minutes I like to be relaxed with a mindset that I'm going to grind down my opponent. I guess in blitz I'm more thinking "explode" the opponent or something 
But in both types I'm polite, and I wont make excuses.
Back in the day I was a pretty good basketball player. Grew up playing street ball in Southern California, and went on to play college ball...yadda yadda yadda. Point is the street baller and the college player where two distinctly different player personalities, which made up the same person.
So it is with chess. As a standard chess player ( 15 mins and up) I'm quite refined, polite, and treat the entire game as I would a fine glass of wine (my college basketball persona)
As the bullet player I talk trash, make excuses when I lose, and am very aggressive and sometimes downright rude.
Anyone else like this?