I say them the sam way you do. I prefer
Eva, it's more interesting and timeless. I picture a dark-haired, voluptuous woman when I think of
Eva, and a fair young girl with
Ava, a skinny teenager.
I don't think I would use
Ava even if it wasn't popular, it seems to lack dimension and personality. I'd more likely use
Ada,
Avis or
Aviva.