1. Performance is supposed to be better (there are threads on this forum with perf testing performance).
2. Tough to quantify, however some have said improved stability as well.
3. Development efforts within MS and audio interface companies are focused on Win 10 - people aren't developing enhancements on older Operating Systems or drivers.
4. I believe it may still be a free upgrade from MS as well, although that may be ending soon.
5. For me, it's something that's going to be necessary at some point down the road, as Microsoft will eventually drop support for earlier operating systems. Win 10 isn't 'new' anymore, it's been thoroughly vetted and tested throughout the industry, so unless you're running an antiquated audio interface that doesn't have Win 10 drivers, you
should be fine.