Argument for me for the K5 would be the small primes as you said (not so much because I think its opticall ybetter but those lenses are tiny, unobstrusive-not much bigger than Leica M lenses), the small and still very good tele-zooms (I do find f2.8 usefull for some subject isolation), IBIS (which again makes much sense with those primes), out of camera color (subjective), very well damped shutter (quiet)....
What argument remains then for Pentax? Small standard primes - ok. Question is what their function is in times when good zooms are at the performance level they are today
But I understand this is all of course personal preferences as well and not just technical .....
For the Nikon D7000 I would see one big argument (for you and it would be also one for me): you allready have very good lenses and could usethe D7000 not only as a smaller body but also as a second body with your D700. You can use the same flash. Also you/we are allready used to Nikon menue structure and user interface. (not so hard to learn the Pentax UI though)
In the end I think both options have so many pros and few cons that you can just decide from your stomach. If you decide from your head you will realize that we both do not need either d7000/K5 but could just use the D700