I'm fairly new to SC, but I know that it's not the language I want to do any serious data analysis in. My own interest is primarily in sonification, so that involves explicit non-sonic data being transformed into control signals.
My thinking at the moment is that it's best to separate the two cleanly - start with instruments that have clear, sonically relevant control parameters, and translate the data stream, whatever shape it comes in, into control signals.
I'm using Python externally to process data streams, generating streams of sonic control signals, and sending OSC signals to SC.
Seems to work, but I'm aware that there is a ton of experience out there and I'm very interested in other people's ideas.
One thing external OSC has going for it is that it scales.