There is plenty of independent testing around the place showing pretty tight comparison between Borg Warner and Garrett GT-BB equivalents, sometimes Garretts can come out strong and sometimes the Borgs can. I am saluting one of the American Subaru tuners who has doing a completely straight up non-biased comparison between GT3076R, GTX3076R and EFR7670 turbos on exactly the same car. The GTX3076R was a little laggier than the GT3076R but made more power, the EFR7670 is yet to be dyno tested but apparently feels very good on the road in terms of boost recovery etc.