Your question seems complicated.
Simply because BOTH of them are important. If my client wants only one I would give an example :
1) Self-consistency focus => Your interface won't attract new people. 10 years ago, it would have been ok. But today, in the digital world where everyone can sell something that looks like yours, it's not ok to avoid "Ease of use" as a whole. Your product will fail and you'll loose tons of money on that.
2) Simple UI focus => Being simple is closely related to the self-consistency. Simple is not "stupid", it's chosing in a "clean" way every things you can do. If your interface is not self-consistent, being simple won't save it from users doesn't understanding what's hapenning on the screen because "Yeah, there you say Payment and after it's Cash Out, is it different?". But still, being simple at first glance doesn't mean "No Deepness". According to some thoeries, to keep the user engage into something, you have to give him an activity related to his competency (Flow theory, CSÍKSZENTMIHÁLYI).
So, to me, there's no good answer to that. Either way, it'll be a fail. Do both, and you'll maybe suceed (but at least your UX will be great)