1. Pulling in tasks from multiple sources. Clubhouse and Things are the ones I use, sadly not supported.
2. Sharing tasks with teammates / seeing what they're up to regardless of the to-do tool they use. This is huge - always wondered why there was no team todo tracker that respected the idea that tasks are tracked in different tools but cross-departmental collaboration is necessary. For example dev work might happen in GitHub and marketing work in Basecamp. Marketing depends on dev but without a higher-level tool pulling in todos from both it's opaque to understand what other teams are working on.
There's a lot of other stuff going on and Sunsama is a pretty opinionated tool (Channels? Estimated/actual time tracking?)
On first blush comparisons to Superhuman are premature...