Wow there is a ton of misinformation in this thread. For the record it has DDR3 which is the fastest current regular PC ram. The PS4 has GDDR5 which is graphics ram. Speed comparisons here are irrelevant. XBOX one also has an HSA processor eliminating the need for both SDRAM and GDDR(I'm probably wrong on that). Though I'll be honest the processor architecture is beyond me it sounds cool though.
As far as used game thing goes it sounds like they have a workaround to allow families to use the game. The game installs in the background so you can play instantly and it is tied to your live account. I'm guessing there is a method to tag live accounts as a family with proof. You can go to a friends house and your game can download if you sign into your account. You will presumably be able to unlink games from your account in order to sell.
Long story short wait till E3 and more info to make a judgement. I'm thinking the XBOX one and PS4 will be very very similar in terms of power, the xbox just will have a bunch more bells and whistles (granted you pay that damn monthly fee).