Welcome to Trulia. I do not know enough this area to provide you with specifics; however a few principles can apply to your question.
I donâ€™t think there is such a thing as the "best real estate company" to work for.
Different Real Estate Companies have different models (Remax and Keller Williams have very different model, etcâ€¦).
You need to match a broker with your own circumstances (do you want to work full time or part time?, do you want to pay more fees and get leads from your broker or less fees and get leads on your own? Are you more of an independent go getter or are you looking for a lot of support and guidance?...)
Usually national brokers offer more support, training and tools that a local independent broker.
You might also want to ask other realtors why they chose their brokers and the reasons behind it.
There were two similar questions lately that could be useful as well:
I hope it helps.