Actually, there's a reason why the curves have their different appearances.
Those curvy arch-ish concrete overpasses are pretensioned concrete structures, those are designed for long spans across major roads or rivers. Stressed cables within the structure improve the loading capacity of the span, and that's done without adding additional weight to the structure.
^The "Other" type of concrete curve is simply the typical U-shaped prefabricated bridge section used in the Neihu project.
^The steel ones are mostly for tight curves (I.E the final turn into the Nankang exhibition hall station or that insane 110 degree right turn at the end of Fuxing N. Rd), Those prolly perform better then the pretensioned concrete ones under those conditions.
btw speedo i also lurk @ the sss.cn Taipei boards, my username starts with a K and has 3 letters , guess who I am