I'm just sharing my personal experience with both. And no, I prefer Flask (WSGI) and Tornado working side by side, in separate processes.

I don't think so. For example,

'I prefer out-of-process approach, where separate set of processes/servers are responsible for realtime portion.'

and

'Tornado is the framework I stopped on.'

and

'Greenlets make everything "easy" at cost of possible issues and allow implicit context switching.'