@Sevs I disagree with
@Cattish. To me the key is the contrast between the two pages before "which one is it". My interpretation is that, between keeping faith with her dad by not doing anything too naughty with her, and doing what she wants which is clearly to move towards hot and steamy, he's asking which should he go with?
Should he give in to, not just lust, but that driving urge to deepen the romance physically, or not? Well, I know which way I'd want to go--that's why you should always be careful what you promise. Don't make stupid promises and you will never have to sully your word.