A couple of years back, I played around with all kinds of these devices.
The SCSI-Ethernet devices that I tested worked well. My favorite is the Dayna Pocket SCSI/Link devices, mainly because they seem to follow the standard SCSI Ethernet protocol -- there was even an Amiga driver written for them. I think there are other Dayna SCSI/Link models, but I like the Pocket models because they can be powered from the 5v ADB port. I was also successful with the Asante Micro EN/SC and Mini EN/SC (the Micro models are also powered from the ADB port). I've yet to test a Focus-branded adapter (in my TODO list).
Next on my preference would be the hardware-based MacIP routers with both Ethernet and LocalTalk ports. The Cayman Gatorbox and Shiva FastPath are the common ones, but I've tested others from Compatible Systems (the Compatible Systems RISC Router 3000E has the fastest processor I've tested to perform MacIP routing for a router with both Ethernet and LocalTalk ports).
Next would be software-based MacIP routers running on an intermediary Mac that has both LocalTalk and Ethernet ports. IPNetRouter is still supported by the manufacturer and I've tested it running on 7.6.1 with Open Transport. Apple used to make one called Apple IP Gateway but it doesn't run over Open Transport; it runs over MacTCP, so if your Mac "router" is running an older system (maybe 7.1), this would also work. If you want the Apple IP Gateway approach, I have an unopened shrink-wrapped copy I could sell ($20 + shipping?).
Finally would be software-based MacIP routers running on systems with only an Ethernet port. You will also need a LocalTalk-Ethernet bridge with this. Some LocalTalk-Ethernet bridges are very picky. I've had difficulty getting the Asante boxes to work. The Farallon and Sonic System devices seem to work, but others have mentioned that there were stability problems with them, sometimes just dropping the bridge connection. As far as the software part (the actual MacIP router), I am trying to resurrect MacGate or macipgw running on Linux -- I've got a small Seagate Dockstar running Debian Linux that I want to use for this purpose.
/pitz