At digicamdb.com, which has some more detailed comparisons for the sensor specs, in addition to the body specs. For instance:
Leica S2 Vs Pentax 645D: http://www.digicamdb.com/compare/leica_s2-vs-pentax_645d/
Canon 5D3 Vs Nikon D800: http://www.digicamdb.com/compare/canon_eos-5d-mark-iii-vs-nikon_d800/
Pentax K-50 Vs Pentax K-30: http://www.digicamdb.com/compare/pentax_k-50-vs-pentax_k-30/, which we could indeed see very subtle differences between the "two" camera(s)! >:-o
So, such comparisons and obsession can always be on-going! ;-p
Related:-
Online Sensor Size Comparison Tool for Different Cameras
Virtually Compare the Sizes of Different Cameras