Today I tested three different external FireWire drives with swappable disks (accepts any 2.5" SATA drive): OWC, super speed and acomdata, with SATA SSDs. Summary: OWC sucks, super speed does its job, and acomdata absolutely rules. Can't wait to try 4TB drives on OS9 someday to see what happens LOL (4TB AFP drives do work... a 5TB WD USB drive I tried did not)
Links for context (for all three products) would be helpful here.
It’s unclear whether you’re referring to external FireWire drives (which come bundled with a drive, and removal/swap is a challenge) or external FireWire enclosures (which may be sold without the disk).
A little over a year ago, when shopping for a replacement for a FireWire enclosure to replace a 2014-era enclosure which failed, the only currently offered 2.5-inch form factor FireWire-inclusive enclosure (FW800, along with USB 3.0) I could find still being offered was from OWC. That enclosure, though in clear polycarbonate, is less sleek a case than its aluminium predecessor, has worked flawlessly with the SSD I added into it.