Is there data or any evidence on it being their best selling computer? I ask because if that was the case, you'd think Apple would be refreshing it as fast as the MBP.
I was absolutely on team iMac until I saw I could get a 27" 4K monitor and dock my MBP to it. Battery life is a non-issue these days as Apple's portables have crazy good battery life. I leave it plugged in all the time when it's in use at home.