Fighting accuracy - Latency measurement (USB)

Hi. I was wondering if someone here knows a way of measuring USB latency. The fact that even though I use the same controller (Dual Shock 2 or Logitech Cordless Precision) it’s considerably easier to perform special moves at least as elaborate as HCB and HCF on the PS2 than on the PC annoys me (HCB/HCF 2x on the PS2 is fairly easy for me, but on the PC is a pain). I got two different USB adapters for using PS/PS2 controllers on the PC, and the inferiority is clear when using either of them. I edited my usbport.sys to have 500 Hz polling rate instead of the default 125 Hz, meaning Windows tries to read the USB bus every 2 ms instead of 8 ms, and it helped to some extent, but still… The only scenario I can’t try is using a native USB controller on the PC instead of requiring an adapter, since I don’t have such a controller, but I’m not very confident the results would impress me (would they?). I have this horrible feeling the polling-driven (as opposed to interrupt-driven) nature of USB may be the worst factor here - I certainly hope it’s not.

Thanks for your help!