What's funny is that the GT2 versions of the Imprezas are identical to GT1's with GT2 only adding polygons. The spoiler becoming thick all around instead of triangles on the mounts, the WRX logos on the sides and trunk being made higher resolution by giving them their own texture area, the hood scoop and modeled exhaust, and proper side mirrors.
Textures were redone in part, but mostly only color adjustments and tiny touches, and I overall much prefer GT1's colors over GT2's, but the changes are a slightly redesigned taillight texture (which is 1px less high/thinner and highlights), rear bumper (narrower plate area with no WRX logo and less black parts, and same for the front bumper.
And even the Impreza Rally Edition got some changes. Them being the taillight design, the scoop, and exhaust.