I have two Dymo label printers. I tried installing the printer using CUPS web admin as well as the Print & Scan under System Preferences. Both printers installed fine. When I print from either the print jobs are sent to only one of the two. The purpose of two printers is to avoid the constant changing of label sizes.
If it helps: my goal is to have two printers available. One prints large labels. The other prints small labels. When i go to print, I am able to choose which printer to print from.