If I have two indexes and use the MultiSearcher will it be faster than only one index with all my documents?

Otis Gospodnetic

That depends on the environment where MultiSearcher is used.
If you have a single computer with a single CPU, then it may actually be a bit slower. However, it could be faster if you're either running on a multiple-CPU machine, or your MultiSearcher is composed of RemoteSearchers, each on a different machine.