I'm not sure enviro/nat park/ is better but a big plus is all the free specialists getting you alot more great people (especially if you get the Nat Park built very early). The 2 watermills I have were built into the last part so prior to that I had 8 preserves. I did actually build the internet but I was so far ahead of the other AI not sure I gained any techs. Built after my ship was launched but yes normally you do need it. Also something else not mentioned. I normally try and build Sistines. helps stop an AI from getting a cultural victory. Also helps expand our borders to hopefully grab more resources.