I'd have to disagree with the boutique comment. You really do get what you pay for.
As far as the sustain stuff, I'm not really sure but I DO know the boutique Vega Trem will blow any Floyd Rose out of the water with more tuning stability and dive bomb ability. I also enjoy Wilkinson bridges like the VSVG. If you're super happy with the higher end Floyd systems, you'll be even happier with the Vega Trem or a good Wilkinson, just saying
And I have 2 guitars with Floyd's. 4 guitars with Wilkinsons. 1 guitar with a Vega Trem. 1 guitar with a Babicz. And of course more. Stay away from Kahlers