I once listened to 18+19 and 20, both, at a dealer. I preferred the sound of 18+19. That said, I would buy 20s, I think. They are simpler and take up less physical space and less gear is needed to run them (I.e., only the Transmitter 1 can provide bass management for the 18+19 combo, which then requires using WISA).
I have a BL19 for sale if you’re in the US and interested. See the For Sale forum.
Let us know what you choose, what you hear and what your thoughts are!