Hi FW
I can't speak for Aberdeenshire (which I will get around to visiting one day soon, hopefully!) but Kilmartin is fantastic... There's just so much to see in a fairly small area! The rockart is spectacular, as are the numerous standing stones, stone circles, chambered tombs...
If you can get there - as I'm sure you know - you'll not regret it. :)
There's tons of stuff that we've been privileged enough to be shown around Perthshire as well, but that'd probably take longer than just a few days!
G x