If I'm remembering this correctly, the Playstation had another large problem in that it used integer coordinates for everything, making it very difficult to avoid the infamous "wavy textures" with textured polys. I think a decent portion of the time, shaded polys were chosen because they ended up looking better, not just because they were faster. If you haven't already, check out the fascinating (and long) developer retrospective on Crash Bandicoot, where (amongst other, more interesting things) they mention their rationale for using flat shading on Crash:
I'm really fond of the PlayStation's brand of 3D as well: There is something really charming about low-res, low-poly 3D, with nearest neighbor texture scaling and 2D "sprites" everywhere. I have some degree of nostalgia for the N64, but that combination of little texture memory and gratuitous bilinear texture scaling is not nearly as appealing.
https://news.ycombinator.com/item?id=2475639
I'm really fond of the PlayStation's brand of 3D as well: There is something really charming about low-res, low-poly 3D, with nearest neighbor texture scaling and 2D "sprites" everywhere. I have some degree of nostalgia for the N64, but that combination of little texture memory and gratuitous bilinear texture scaling is not nearly as appealing.