I assume from the post’s that English isn’t your native language? That’s fine, no problem there, but helps us to understand why you don’t know the jargon, slang, terms that most typical rail fans use.
Another thing though, is you are asking for a very specific answer to a question in which there is no answer.
There are no specific “mine locomotives”. Everything from SWitchers, to General Purpose (GP’s, GeePs), to Special Duty (SD’s), to any combination of drivers on steam locomotives were used for mine and mill work.
What is “best” is also a personal subjective term. What makes them “best” is based on opinion, and can and will vary from person to person. This makes it your choice. If you like SD-45’s, then by all means, use them to switch your mines and mills, cause they’ve been used on the real railroads to do such. That applies to pretty much any engine/locomotive you can think of.

