If you are going to upgrade, get the Biss-C at €129, not Sincos at €120 (and out of stock.)
I upgraded my Small Mige 10,000ppr encoder with a Biss-C. Is it better? Yes. Is it €129 better? Maybe not. It was an improvement, but I wasn't blown away. However, I'm very happy with my Small Mige/Biss-C.