I am still with my 2009 Mac Pro (spec as per my signature). Sierra is more smooth then El Capitan, less bug for me as well.
On my own computer, 10.11 has USB 3.0 bug (unable to recognise my USB 3.0 hub, card reader), GPU bug (not 100% sure it's from GPU, keep working on this with Apple Engineer for few months, and but they believe it's the GPU driver's bug, but never confirmed and fix the issue), slow shut down bug (may take 5+ minutes to shut down).
With Sierra, USB normal, GPU normal, shut down normal......
And I didn't do any fresh installation since 10.7. So, if there is any "my own rubbish" in the system causing the 10.11 malfunction, all those rubbish should still on my machine now with Sierra.
However, what I realise is that Sierra definitely use more memory than El Capitan. May be my 48GB RAM helps, therefore my Mac can works better in Sierra.