Certainly, all the comments of "External TRs are too powerful!" sound like they're from Apollo players. Since the Strength of the external depends on both AI and player cities, on anything lower than Soyuz, the Externals are actually competitive with optimized Internals, and on Mercury, they're hardly worth plying.
Even at the lower levels, there is still the issue that you get an extra route from Autoplants and AIs do not.
I'm curious if the decreased TR effectiveness in lower levels is enough to offset the weaker AI bonuses? The problem, centrally, is that the AI is not a challenge -- on any difficulty -- and even if internal TRs are more interesting and competitive on lower levels, if the AIs aren't more challenging then I don't think it really matters whether I play Apollo or Gemini.
I mean I enjoy theorycrafting a bunch, and unlike a lot of civ fans the scifi flavor really does it for me. But there's a limit to how much fun I can have coming up with strategies to beat an opponent that just rolls over.