Not much to say, just replaced some R2 series fans in my define R4 with some R3 series fans, and the cables are 15cm(50cm vs 35cm) shorter and don't reach my motherboard connectors. It's not the biggest deal, i've hooked them up to the fan controller in the case instead(push enough air set at 5v), but it was an oversight on my part becase i would have preferred them hooked up to the motherboard(using voltage control). Visually and performance wise they are pretty much like for like, but i honestly prefer the sleeving and extra length of the R2s and naively expected the same from the R3s(it's on me for not nitpicking and reading more closely).
My fault is assuming it was a like for like change(one series along), i didn't anticipate the cables not reaching(being shorter) and it's a little ironic that fractal branded fans can't reach across a fractal branded case for the motherboard headers.
Minor inconvenience and unintended cost, i'll sort it out with some extensions, but honestly, why Fractal? Was that tiny amount of extra wire a huge cost saver?