Very, very different tools, though they cover similar areas.

Temporal - if you have strict workflow requirements, want _guarantees_ that things complete, and are willing to take on extra complexity to achieve that. If you're a bank or something, probably a great choice.

Oban - DB-backed worker queue, which processes tasks off-thread. It does not give you the guarantees that Temporal can because it has not abstracted every push/pull into a first-class citizen. While it offers some similar features with workflows, to multiple 9's of reliability you will be hardening that yourself (based on my experience with Celery+Sidekiq)

Based on my heavy experience with both, I'd be happy to have both available to me in a system I'm working on. At my current job we are forced to use Temporal for all background processing, which for small tasks is just a lot of boilerplate.