Yes in paper it's a weaker hardware, but lets not forget when game developers work towards the strength of a particular console, the games start to truly shine. When the PS3 came out it's GPU was considered very weak next to Xbox 360, but when the developers like Naughty Dog, Sony Santa Monica, Guerilla Games & Sucker Punch started to work towards making the best use of the cell processing units, it resulted in some of the best games of last generation. Games like Quantum Break from Remedy and other exclusive titles that are going to come out on the Xbox One will truly shine.
Why are you saying PS4 has stronger hardware "in paper" like it doesn't already show itself in real games. As for PS3 having a weaker GPU than 360; it had Cell which made up for it. Does XBone have anything to make up for the power difference?