I wish I could get all of my thoughts down correctly and at one time ... oh, well.
20th-21st century ICE technology is creaming the BTU in terms of speed and weight.
A typical BTU combat rated ICE engine does, however, get 1,000 km in range. I would imagine they're a bit better on pollution, too.
Once you start piling on modern (BTU) control equipment, weapons, and especially BTU armor everything changes (How is this game not based on RL stats! *JOKING*).
gonna need some compromises for my other designs (still surprised how the Huey came out really good imo, but then again it was a sub 5t design using infantry scale weapons)