TWOK is better IMHO than TUC is.
TWOK is my 2nd favorite Star Trek film. It's got everything, action, drama, good character moments, emotion, great special effects despite having a lower budget than the previous film and an iconic villain played perfectly by Ricardo Montalban. Meyer really gets the most out of his characters. In fact my only real complaints have to do with things I've noted in the past about plot holes in the details of the story that don't hold up with close scrutiny and casting choices of Khan's band of merry supermen (specifically how they suddenly became an 80's Swedish hair band).
I find TUC to be a middle of the road Star Trek film. The overall story is good. It shakes things up with the prospects of peace between the Federation and Klingon Empires, and the basic conspiracy idea, sabotage and framing of Captain Kirk were good as well, the special effects were good, and there is a great battle sequence at the end. And while the role of Chang is a bit caricatured, Christopher Plummer is still a great actor and in some ways overcomes some of that. Plus, I liked the added touch of the patch
nailed to his head. Very Klingon

But I have serious issues with the overt bigotry, especially among the command crew of the Enterprise. Spock alone is his old familiar self. Captain Kirk I can understand. He's had the most history with the Klingons and, well, Klingons murdered his son and they've been after him since the events of TSFS (in universe about 8 years prior). But the rest of the command crew is very much out of character for me. I can understand caution, even some distrust. But I would also think there'd be some hope, and at the very least an open mind. That is something that always bothered me about TUC and does drag the film down for me.
For the record my favorite Star Trek films are TMP in first place, TWOK in 2nd place and FC in 3rd. TUC probably falls around 6th or 7th place. My middle films do tend to fluctuate. Only my top 3 and bottom 2 are pretty firm (bottom 2 are Insurrection and TFF--though I don't hate any of the Trek films, just that somebody has to come in last and those 2 are unchanging, though I've noticed a new appreciation for TFF over the years, if they'd just fix the damn special effects--but that's another thread

).