Yes, this is exactly my point: IQ versus DoF. The 5D certainly has 1-2 stops narrower depth of field for a given angle of view; there is no question of that. It is a matter of how this weighs against the IQ (and weathersealing, and ergonomic, and . . .) advantages of the K5.
Note that I did finally edit my previous post on computer; my phone was giving me trouble. :-(
Well, I used to have a K10D and a 5D, and I can tell you the 5D beat the pants off the K10D in terms of AF speed - at least with the lenses I had, which were the 50/1.4, 100/2 & Tamron 28-75 for the 5D, and various lenses including the 21/3.2 (fastest of the bunch), 35/2, 43/1.9, 50/1.4, 77/1.8 and 18-50/2.8 (Sigma) on the K10D.
K10D was very slow, K20D better, K-7 better again and K-5 is worlds away in AF speed.