Back in the day loading a video game was a very private, safe almost sacred experience. The world melts away and it's just you in the fantasy world the game presents to you.
For this reason I'm going with the boring old model of pay once, own the game. Everything I read says free + IAP is the way to go for maximum return, but I really feel something crucial is lost when you make the player contemplate their credit card bill while supposedly experiencing escapism.