My understanding is that Tim thinks de novo AI is very probably very near, leaving little time for brain emulation, and that far more resources will go into de novo AI, or that incremental insights into the brain would enable AI before emulation becomes possible.

On the other hand, FHI folk are less confident that AI theory will cover all the necessary bases in the next couple decades, while neuroimaging continues to advance apace. If neuroimaging at the relevant level of cost and resolution comes quickly while AI theory moves slowly, processing the insights from brain imaging into computer science may take longer than just running an emulation.