I think this is going to shake out only after 6 to 12 months of sales. If XBone is running away with marketshare and software sales, the PS4 version will get little love (low impact enhancements that take up little time to implement).
If the platforms are very close or if PS4 is ahead, then I suspect there will be more incentive for publishers to make their PS4 titles stand out and the difference between the same 3rd party titles between platforms will get larger.
Ps3 games was held back not by xbox360, but by being a very difficult peace of hardware to make games for. Ps4 has no such drawback. Result: Games on ps4 will look better as long as the rumoured/confirmed specs tell the whole truth about the real power in both consoles.