Cant say I have ever noticed a difference to be honest. I have two external SCSI units on a chain along with my ZIP and CDRom. Prefer external boxes on an internal SCSI card cus they are easy to expand and change. There is only a slight slow down at boot as they talk to each other, but I do like that they are on their own power and cool out of their own box. I have machines like the A4000T that run totally on SCSI and they work fine with the drives inside.
As to the technical issues I don`t know. All I know is what I get from them and they have served me well without fault. Internal IDE's are another matter... have had them fall over no end of times, especially on the 4000ds and towered A1200s. I have a stack here of busted IDE hard drives.... Strangely no broken SCSI drives.
scuzz
http://www.commodore-amiga-retro.com
