I know it's an old chestnut, but I have made a video comparing Synchro Express and Blitz Turbo and uploaded it to YouTube:https://www.youtube.com/watch?v=NClOTTPH-CI
For test purposes I copied the So Watt MegaDemo and verified it using FastCopy 3.
For the record the Synchro Express caused 13 RNF/Seek Errors (all on side 1!) and and Blitz had 19 RNF/Seek Errors and the demo wouldn't boot!
I couldn't find the "Slower By Jobil" copier on my Blitz Utilities disk. I had the Unitec one by Jobil but it didn't work too well. I actually have 2 Blitz Cables, one from 1990 from Power Computing and an unknown one I got with the Synchro Express on eBay about 7 years ago. This is the one I used in this demo.
From memory my STE was more reliable with Blitz with an Epson drive back in the day than this STFM which I think has a Mitsumi drive. It still freaks me out to see the 2 drives working at the same time like that! Anyway I hope you like the video.
Still got, still working: Atari 4Mb STe, 520STFM, 2.5Mb STF.
Hardware: Cumana CSA 354, Ultimate Ripper, Blitz Turbo, Synchro Express II (US and UK Versions).