I just upgraded from the 2015 MBP 13 to the 2020 MBP 13 gen8. It is noticeably faster in pretty much every way, runs cooler, and is slightly smaller physically. My 2015 served me extremely well, but it was used hard for 5 years and it was showing.
I debated between the gen8 and the gen10, and if I thought I was going to go another 5 years before upgrading, I would have gone for the higher tier, but with the rumored switch to ARM I’m guessing it’ll be more like 3 years with this machine so I decided to limit my potential depreciation. Also the iGPU performance does not matter in my workflow. If it matters for you, then of course get the gen10.