i used to have a 172 cup, and have driven the 197.
the 197 rattles less, is better screwed together, has a better quality interior, optional recaros are fantastic and the 197 looks awesome.
however, its less punchy the the 1*2 due to slightly more wieght and 6 speed gearbox, ur always changing gear.
Its also a tad less 'point and shoot', it all feels far more refined. A worth upgrade tho, go for the R27 for the cup chassis and graphics and ltd edition-ness.
Or do what im doing and hold out for the 197 cup to see what thats like.