it will make a difference, sure, for those who love third party games or if the difference is dramatic enough to sway people. But I don't believe in the latter as being weighted as heavily.
As long as Playstation is anywhere in range, even as far as 33% down (the difference between XBO and PS4), the games will sell the system.
Sony has managed GOTY hit, after hit after hit. There are a subset of people that are drawn to those games. No amount of graphical difference is going to make up for lost content.
There is a subset like myself who mainly only enjoy MP gaming, in which Xbox is a better fit for me, but if you're looking for those single player experiences, you're going to see a lot of people not give a damn about the power difference. (ideally MP is also where you want the most power honestly speaking this makes the most sense - higher frame rates, resolution etc)
And with the cost of these coming consoles, it's not going to be cheap to own both.
I don't believe the lack of marketing is a result of necessarily being fearful of being down on power (though it would obviously help to be the power leader) but I largely suspect that Xbox's platform now to the future is providing value in a way that could detract the messaging around Sony's strength around exclusive titles. There's just a lot of value there for relatively nothing. You can fund a full family of gaming for very little and have a selection of titles for different age groups in an increasingly large library spanning 4 generations with what looks to be enhancements of all sorts.
So while Sony may come across as the quality king, some people are going to be really drawn by the AYCE model. They are likely working on platform plans before they need to announce any of their hardware, whereas Microsoft's platform plans are fairly well known as they are already in place, so they only really have hardware to talk about.