X1 has 7% faster GPU clock (this will help the entire front end which should be identical to PS4), 9% faster CPU clock, almost certainly an extra half gig of RAM currently usable by games, in theory a good deal higher peak bandwidth (with strict unfortunate 32 mb restrictions of course). It's not all cut and dried. Those could help close the 40% GPU gap in other ways (though it might be hard to pinpoint any in the case of Destiny). I remember in the Xbox architects interview, they mentioned having prior experience with GPGPU that was more bandwidth limited than compute limited. And I also remember in Anandtech's Haswell review, where Iris Pro's EDRAM really helped was GPGPU benchmarks.
I'd say more to the point Destiny still has prior gen roots. IMO it looks very very nice, but it's not really stretching next gen legs. I'll be more interested in the really heavy duty games that will really load the hardware coming up, Far Cry 4 and GTA V come to mind.
In the end people need to understand developers are not console warriors but they're going to take the easy way out. Best case for PS4 is probably typically going to be 1080P vs 900P, as that's an easy way to do things, key word, easy. Plenty of multiplatform games back in 2003 didn't utilize Xbox's vastly superior capabilities vs PS2. Almost all of them, in fact. Rare was the Splinter Cell that looked a generation better on Xbox.
Anyways maybe some more technical people could speak to this question that seems key here, if you have 40% more shaders sitting there whats some easy ways to throw extra visual goodies on screen? My guess is it wont actually add that much noticeable to the visuals though. Things like SSAO. But it could satiate some forum warriors.
You could make an argument making more powerful hardware is a losing game, because multiplats will just default to the lowest common denominator and the more powerful hardware you as platform holder spent extra on will typically not be utilized. I dont agree with it on the whole (imo PS4 is selling well almost entirely because of it's hardware), but it's a sentiment that has some validity.