Below please find an Infographic comparing the current summoning portals, rates, stated odds and possible cumulative odds for certain summoning increments.
(update 2020-09-17:Ninja portal and Tavern portal v2)
(update 2020-12-03: Updated Tavern portal v3 odds and Atlantis v2)
(update 2021-05-24: Updated Challenge Event w. Trainers and Underwild Summons. Note skipped v4.0 public release but had internal copy)