This is way too long given the limited scope of the topic and its relative simplicity. Eidolons come in a few basic categories, and after that the only difference between them is the summon effect and the element. The summon effect is generally a very minor consideration, except for Behemoth.
This is pretty misleading. SSR eidolons other than the +100% eidolons are nearly worthless in the long-run without multiple LBs. Since what to start with is probably the single most important decision most players will make, there's no room for confusion. If in doubt, just link my rerolling guide. I can update with an explanation of why the +100% eidolons are optimal starting picks if needed.Also, HIGHLY recommended to Reroll for the Gacha SSR Eidolons (particularly the 100% ones)