I suggested a new thread as user(s) will need to show make,model and what firmware the unit has.
You may also have to post what SCSI controller is used & speed if the processor to get a rough idea which unit is the fastest as some user(s) may want to use CF as their main drive (bootable) if its fast enough to use as a main drive.
All of the pcd-50b/60b's i sold had the latest v1.28 read/write firmware and the pcd-47b's had the latest m3.2 read/write firmwares.
the MFG suggests 4-5MB/s max speed on the card readers and i attained 3.9MB/s with the csppc and a high byte adapter and a fast transcend class 10 SDHC card. The cf came in slightly under. Unfortunately i spent more time testing for compatibility on different controllers than max speed.
They aren't the fastest thing around,but for hot swapping and just being a handy low power quiet solution they are great.
The acard + ide-cf adapter is quicker,and you will likely attain max speed,but no hot swapping. On slower,older controllers it is likely not to be faster than the card readers.It will shine on good scsi controllers like the warpengine,cyberstorms,gvp 4060,etc.