I can’t help you as I only used CalyxOS so far, but I am prepared for a nice weekend with a lot of popcorn.
But in general I think it depends on your preferences: CalyxOS has the advantange that it is all about OpenSource while iodé has closed source parts (which are a selling point) with their built-in adblocker.
Calyx works completely transparently on github/gitlab and they provide changelogs, iodé does not.
Iodé is (as far as I know) based on LineageOS, Calyx on AOSP. CalyxOS works with OTA, but as far as I know iodé does so, too.
There are a lot of differences, and they arise from the different philosophy. I think you would have to clarify for yourself which points are important to you.
About bricking: actually it should not happen anymore, but occasionally reports appear in the CalyxOS channel. Especially, if I see it correctly, with a return to Fairphone’s stock ROM.