My first choice was Emery. However, from the moment RM was sacked it was clear that Koeman was first choice(Esk has repeatedly pointed this out).
So, we have signed our prime target , which is a plus. I think that signing a manager from another Premiership club , and not a very big one in spite of what Southamton fans think, is not very inspiring and that is causing some apathy compared to the more exotic Emery. If Sevilla had lost to Liverpool in the recent final I wonder if I would be as enthusiastic about Emery...thankfully I don't have to find out.
But, and I readily admit this, there would have been obstacles faced by Emery which would have made his job more difficult. Language, new country, new league, new culture. Certainly not insurmountable, but difficult nonetheless.
Koeman should already have a decent knowledge of the Everton squad from playing against them.
It is likely that he will already have a knowledge of the youngsters coming through the academy as well. He already knows the Premiership even though it is possible that he may be revising the level of his transfer targets upwards if the stories about funds available are true.