For those whose teams are alright enough such that any particular SR won't really strengthen you, you may instead focus on fulfilling requirements instead.

For Thunder, if you do not have a 2nd defender, getting Kingu would allow you to clear that floor in tower quest that asks for 2 thunder defenders. Also, it is one step closer to 3 defenders for both water GO if you like to stick with element advantage. (for the 3rd defender, if you don't pick up Raiko or Athena, you'll have to wait for the SR hime Hlin in late May.

Similarly, for Fire, if you need a 2nd defender for wind tower quest (assuming you have Kishar as your first), you should be able to choose Fire Eligor.