I find that with Terraforming Mars, even without the Turmoil extension, you can have card combos that add real complexity to the strategy, and you need to regularly adjust due to the luck of the draw factor. Turmoil adds an extra layer that makes your path even more tortuous. With Gaia Project, I feel everything is more streamlined. Terraforming doesn’t feel heavy as such (I absolutely love it, I have played it so much) but the variety of paths seems larger than on GP. I also have to say that for me on Terraforming, it’s more satisfying to create a coherent game, with choices that make sense for the corporation or the situation, than actually winning. I treat it almost as an RP game.
Horizontal of course, we are not savages!