There are mixed results for the GT-RS too, like the difficult to reproduce >300rwkw claims.
There have been a number of variables from R32, R33, R34 turbine and compressor housing variants plus whatever GCG are doing to them internally from the early days of the "500hp" version that surged to the latest version that seems to be well sorted.
Having back to back tested them I am convinced the GT-RS will come on ever so slightly (very slightly) earlier but the price differential makes the GCG turbo the best value in the 450hp range. If you want more power I think this makes an orphan of the GT3071 on an RB25 as it makes more sense to jump to a GT3076 if you want more power.
DaleFZ1 has back to back tested (on the road) a HKS2835ProS and a GT3076 56 trim comp with 0.82 internal gate he might be able share his experience.
Any of these turbos will be absolutely fine.