I did some spreadsheet calculations comparing farmable SRs (from Disasters) and SSR event items and came to the following conclusions:
https://docs.google.com/spreadsheets...it?usp=sharing
- SSR eidolon max stats exceed the Disaster eidolons (LV90) if you limit break at least once (to LV55). This is very achievable for anyone spamming Expert, even if you don't use stamina potions.
- SSR weapon stats scale very similarly to the Disaster weapons level-over-level. If you don't limit break at least twice (to LV100), the stats won't be significantly better than a maxed Disaster weapon (LV85). One copy of the SSR weapon is useful for the added Burst damage when equipped on your hero and fighting the opposite element; otherwise you'll probably want to use your limited resources on LB'ing the eidolon. If you plan to run a Dark team AND will have a hero that can equip the weapon, additional limit breaks on the weapon to buff the Burst damage even further could be useful; I don't have data on how the Burst damage on a partially limit breaked SSR compares to a fully limit breaked disaster weapon.
In short, if you're running a team of the same element as the SSR weapon and will have a hero that can equip it, focus on getting multiple copies of that. Otherwise, focus on getting multiple copies of the SSR eidolon.
Also, the stamina potions are self-refunding. Buy two of them every day and use them now or later to run events additional times.