For the most part, I prefer shorter anime. Usually around 12-14 episodes is good for me. However, in some cases I'd want it to be longer. For example, I want Fairy Tail to be long because the manga is on-going and I want the anime to follow it.
Fairy Tail has incredible fight scenes. They are very fast paced and are close to the manga. There isn't much talking during the fight either like with other anime. At most, they exchange a few words and go back to fighting.