There's a financial disincentive to make one version look significantly better than the other, generally. If both console bases think your game looks great, neither feels slighted (except for the crazies who insist their version has to be better, because their console is better, because REASONS).
Even then, without consciously adding effects that make 2 versions disparate, there will be things like consistent framerate and less tearing that are just a side effect of running on better hardware and not necessarily coded for. And apparently a few fps is enough to sway many Gaffers toward one version.
Tinfoil hat time, but if Microsoft goes the no-used-games route and Sony doesn't, what are the odds some third parties willfully make their games better for the Xbox?
I don't know, but those devs will be skewered by the gamer community, and Digital Foundry will either out them for it, or go silent. DF has a precedent of questioning why developers didn't take advantage of some of the hardware features of the 360, when the PS3 version ended up superior.
We don't know anything about Durango though, unless you consider rumors (possibly based on outdated information considering SuperDAE may have been telling the truth) to be a worthy point of comparison.
Well, yeah. It's a given that all this discussion is based on rumored specs until we get official ones. It's all hypothetical talk that interests some people. There was a whole bunch of speculative comparisons based on Sony going with 4GB of GDDR5, and that obviously changed.
Just listening to Patrick on Giantbomb and he said that 3rd Party support for the consoles will be a "blood bath" and certain companies are aligning themselves with certain consoles. That timed exclusives will be a thing.
That's the "special sauce" that could actually trump inferior hardware. Nintendo started next gen moneyhatting Monster Hunter and Bayonetta. If Sony or Microsoft(more likely of the 2) were to pay for timed-exclusivity of the first next gen COD, it'd be a huge blow if not game over for the other platform holder.