I still run an aging R210ii, and it’s been great. Mostly…
If you’re going to use the server for storage (or I/O heavy tasks), you might be better to get the Optiplex since it has SATA-III (6 Gbps) and the R210ii only has SATA-II (3 Gbps). The R210ii also only has one PCI-E slot which limits expansion options.