I have tried all of the finish options noted above and they all work in the short run. In the longer run there are trade-offs with each.
A Don Beale two piece (carbon ferrule) I purchased was used three times, by two different competitors (not me) in Greenland competition. Don used epoxy for the surface coating of this solid WRC paddle. Epoxy is nice in the short run but since WRC is a softwood, it eventually develops bruises from use. At the site of bruises the epoxy surface is breached, allowing water intrusion. Eventually there is water staining there and over a longer time, the epoxy starts peeling. This paddle had extensive staining from it's heavy use and some epoxy flaking. I stripped the epoxy off, lightly sanded and stained it to hide the water staining. It was oiled it with 100% tung oil. In it's restored state it is as attractive as a new paddle. Restoring it was a lot of work, a consideration I have about using epoxy finishes on solid WRC paddles when, in my opinion, they don't really need it.
Oiled paddles scratch much easier than epoxy coated paddles and need much more frequent refinishing. Usually thats just light sanding and another coat or two of oil. This finish is much easier to restore than epoxy. For this reason, on my solid WRC paddles I prefer oil finishes.
WRC paddles can be left unfinished and they will turn a nice muted gray tone. Sand them a bit smoother and sanding any rough patches that develop from water raising the grain will eventually leave a very fine surface. This results in the least slippery paddle surface.
Paddles made with a number of laminations are good candidates for epoxy coating. Epoxy will reduce the chances water intrusion causing delimitation from differential swelling between the layers of wood. I made 15 hollow WRC paddle blanks for a ConnYak class and specified they were to be epoxy coated on completion (at home) for this reason. The two that developed some delamination were not epoxy coated. After being reglued, they are now fine with their (new) epoxy coating.