The comparison between xbox one and ps4 is fairly easy. It's like building two PC's based around the same cpu but one you fit a good mid range graphics card with high speed memory and the other you go with a basic entry level graphics card and use slow cheap memory. Once setup playing the same games you realise the weaker PC has terrible frame rates that don't match the better pc so you start dropping graphic detail and lower the resolution to improve the frame rate. The memory system still struggles though under load and you get severe frame rate drops. You have the choice with the better pc to either match the weaker pc in graphic detail and resolution and enjoy fantastic frame rates even under load or you can judge how much better you go in graphic detail and resolution before that PC also suffers from frame rate drops.
It's just the same with xbone and ps4. The issue developers have is setting the right balance. If they keep setting the ps4 resolution and detail too high then it could end up with a worse frame rate than xbone and in real terms be an inferior port to play. The extra performance of the PS4 doesn't guarantee a better game but realistically the ps4 is much better setup for the future. Fully optimised it can match good mid range PC's today, perhaps normal mid range pcs next year and entry level pc's in four years lets say. The xbone is perhaps already at normal mid range pc's and will be at entry level a year ahead of the ps4.
Xbone is destined to have the weakest versions of pc,ps4 and xbone multiformat games for this generation. You will be paying a comparable price to ps4 yet getting an inferior version. PC owners will have the lowest possible software price yet the potential for the best actual version of the game technically. However you look at it, the xbone represents very poor value at its current price and needs to be sub ps4 in pricing realistically.
The belief that somehow developers will make the extra effort to make xbone versions comparable to ps4 is not realistic especially as the ps4 is the leading format of this generation. Any game that is actually equal or inferior on ps4 compared to xbone is going to get a hugely negative reaction and a certain drop in sales because of it. It's possible Microsoft may have some influence to do this early on but I don't think it will continue. Microsoft is constantly pushing to downplay the technical differences for the very reason that there are technical differences.
