Breed or rune gems?

So say you want a certain mystery talent for your monster, would you rather breed until you get the one you want, or wait for rune gems and take your chances? The rune gems are pretty rare and don't guarantee you get what you want, but breeding gets expensive and still doesn't guarantee anything. So, any thoughts?

Doesn't really matter. Whichever method you use, the outcome is random.

At the moment, I'm breeding to get my favoured mystery skill on Flight. However, I am also using Ultimate Rune Gems on him as I've taught my other monsters (in my ladder team) the preferred skills.
As long as you can do either, do it. The faster you get what you need the faster you can go for your next mission!