Depends on the car. Some NA's I wouldn't FI with a bargepole (AE86, AW11, McLaren F1, Spoon Hondas), some I wouldn't hesitate (generic blahmobiles, classic VW's and the Fiat 500 because they're so much more fun with >100bhp). I love both for different reasons, uses and depending on what kind of mood I'm in.