A65 throws away something like 1/2 stop up through the viewfinder, so it's at a disadvantage to the K5 to start with. Try comparisons of ISO here [19 at www.dpreview.com] and you can see for yourself.
On the outdoors front ... the K5 is known to rule. Weather sealed and made from magnesium alloy, it's body case is allegedly built by the same people who built the M4 Sherman Tank. Rumour has it that they used it on the last shuttle mission to space, but dropped it; it fell onto a farm in Kansas six months later and is still being used by Mr McDonald, although NASA have asked for it back.
