. I hear so many people say the Klingons of TOS were 2D villians, but damn... Just watch Errand of Mercy and it's clearly not true. Every scene with Kirk and Kor is fantastic and infinitely entertaining. The Klingons in TOS obviously had some brutal aspects to them, but they also seemed very patient, calculating, philosophical, and even reasonable at times.
So i'd say "Kor" but i'd also say, either way you're in for a good time. Errand of Mercy and Day of the Dove are both good episodes from either end of the TOS run, and in large part thanks to the guest actors giving stellar performances.
And remember, "Only a fool fights in a burning house!"