If you check out dxomark, the summilux is ahead in terms of sharpness but not by much. Again, if size is compared, the summilux is smaller. But, if price is compared, the 25/1.7 wins hands down. Photo quality of 25/1.7 is quite close to the famed 20/1.7. It also has very nice rendering too wide open. And it shoots much much faster than the 20/1.7.
If size is absolute importance, like me, the O25/1.8 it is.

Otherwise, a Summilux is still a Summilux. You won't regret having this.
Always go for the latest model if you can afford it. Choosing between EP5 vs GF9 quite simple to me. EP5 is a much higher-end model. I owned it before and I really liked it. If you don't mind it's an older model, go for it!

GF9 is more a selfie model just like the GF8 and is a good starting unit if your just into m4/3 and it will take very nice pictures too, though not as advanced as the E-p5.

Whatever your choice, both are good models.