Selene is hands-down better than Eos if you can handle healing.

They heal about the same, minus the 120s cooldown 20% potency buff Eos gives for 20 seconds (rarely ever need it).
I have never had to use Fey Covenant.
Whispering Dawn is nice but overkill if you have a WHM in the party who has used Medica II; if Medica II isn't enough to top off the party for now then what you need is instant AoE heals via Indom or Emergency Succors or Medica/Cure III, not an AoE regen.

Selene gives a raid-wide Esuna and a 3% Attack Speed buff every 60s for 30s. Over a long fight the effect is noticeable and it also helps you apply heals and shields quicker and lets casters better deal with dodging and etc.