UK Digital Photo Mag Says 5d3 Better than d800

You are correct. If you make the jump from APS-C to FF, then your investment in glass (if you were smart and bought FF glass) will dominate your decision making process. P&S to FF is likely a very low number.

Let's say if you have no investment in FF glass, then the D800 is going to be the more likely buy IMO. Whoever said the megapixel wars were over is about to be proved wrong in this case.