Selene is better for support and dps but I dont think she is better in term of healing.
Yes, mathematically she can give you more healing during her 60s of Fay Glow during two minute period. However, no one spam heal for the whole 2 minutes.
Eos Illumination is only 20s. Together with Rouse, you can get thru a very spkiy period. (high stack boss turn 2, high stack ads or accidental high-voltage, turn 4,...)
So I personally think Eos's healing boost is more effective for healing. Not to mention it is more mana-friendly.
There are use for both. I don't think one is definitely better than other. It also works with the play style of player: want more control and use embrace manually? Selene. want to keep your cool down and react appropriately? Eos.