To add to a curernt thread drift discussion, modern Sora(so anything with 2 paddles and no thumb button) which is 2 generations and probably 8 years of product, shifts perfectly fine and stays correctly adjusted just fine. My family has 2 bikes with modern Sora shifting, 2 bikes with Tiagra 9sp shifting, and 2 bikes with Microshift 9sp shifting.
All of it works and stays perfectly aligned once it is properly set up and dialed in.
Further, I am responsible for keeping 6 road bikes in good working order that have modern Sora and modern Claris. The shifting accuracy of all these is probably the easiest thing to oversee- none of them go out of tune unless something happens like the bike is dropped on the drive side, a wheel bumps into an RD, or something similar like that.
I am not saying someone else is 'doing it wrong' or is incapable of setting up a bike properly. There could be some wonky 1 off issue that they were subjected to. My only point is that overall, Sora stays in tune for as long as anything else I have ever used or work on.
JochenRindt - if you buy Shimano R3000 shifters, they will work perfectly with your 9sp rear derailleur, but they will not work perfectly with your front derailleur. That model shifter requires a new front derailleur. I have read people have kludged together a setup that makes front shifting work well enough, but I have also read about others ultimately having to buy a compatible front derailleur.
As for which should you get of your listed 2 options...I would say the biggest differences are cable routing, shift paddle design, and cost.
- cable routing for R3000 shifters is under the bar tape while Microshift R9 shift cables come out the side externally, just like your current shifters. If you like one more than the other, then thats something to consider.
- shift paddle design is different. R3000 uses the shift lever to get to easier large cogs and the single paddle to get to smaller cogs. Microshift R9 has a dedicated brake lever and then 2 small paddles for shifting up and down. I like both styles, but if one appeals to you more, then that is also something to consider. Shimano shifting is more fluid/smooth. Microshift shifting is more abrupt and deliberate/solid feeling. Basically, they feel different and that matters to some.
- Shimano R300 shifters cost more and you will need to buy a front derailleur. Microshift and Micronew(effectively same thing) cost less and are fully compatible with your current derailleurs.