I have upgraded to Sierra again finally after trying it a while back and reverting to El Cap.
I have 2105 Rmbp, i7 16gb ram 512gb SSD, discrete Graphics and yes its slower than El Cap, for me anyway. Graphics are more stuttery, loading up from being off is quicker though, but UI is slower.
I concur (2010 iMac) – there must be some other factor at work: suggest running EtrecheckI have no performance problems on Sierra with an "old" late 2012 mbp - sure I wish I had an SSD but other than taking a bit to start up - I have no performance complaints - and it certainly hasn't gotten any worse with OS upgrades