Which case of casting upheaval grinds your gears (http://officialfan.proboards.com/thread/499593/darren-tori) more?

I still don't like the new daughter on Last Man Standing.

Neither one gets me terribly upset. It happens sometimes. It's happened on "The Fresh Prince of Bel-Air" and "Family Matters" and I love both those shows just fine. (The cast member getting replaced by someone else.)
The revolving cast thing happened a lot on "Saved By The Bell: The New Class" and "Hang Time" and "California Dreams"- but I still love all those shows just fine. And at least in those cases, it actually made sense. The shows are all set largely at high schools and in real life, people move all the time- not everyone stays at the same school and finishes there. So it seems logical that sometimes some of the main cast might move to another city and go to another school, etc.
In any case, it doesn't really bother me too much.

Definitely recasting. Fresh Prince of Bel-Air and Family Matters are perfect examples of how this pisses me off.

It makes the show that much more unrealistic. You really think no one's going to notice that you replaced a dark skin person with a light skin person without any explanation.

I can deal with a revolving door of characters, if done right (like on Cheers for example).