After having played the DMM version for another week, I think the only SSR Eidolon draw I would consider keeping would be Fafnir(you won't outlevel them; it's still one of the most useful summons I see with the DMM version having been out for almost a year). Behemoth is decent, but, personally speaking, I'd probably rather have an R kamihime of a chosen element over it.

As far as SR Kamihime go, I don't really think there are any 'bad' picks, just go with the element/one you like most, thematically. Aside from the elemental(no light/dark) SRs you get from the main story, getting more/better Kamihime is your primary bottleneck to getting stronger for the early/mid-game; so starting with an SR of your choice is a huge boon.