Radeon 560 vs Radeon 555
Looks like the 560 massively outperforms the 555 in benchmark testing:

http://gpuboss.com/gpus/Radeon-RX-560-vs-Radeon-Pro-555
And looks like it has twice the VRAM (4 Gb vs 2 Gb) which to me makes it a pretty easy decision.
FWIW - I'm a graphically-intensive applications user, and having a GPU with more VRAM means better performance from apps which target GPU processing, so I'm not a typical use-case.