For me, Son is more finishing the move than Lamela, who I feel assists the play. I feel we need that extra player deep MF and a player who links up and can take players on as with Lamela. Son will create goal scoring efforts which may be suited later in the game if we need to stretch them a little (if they are on top). They will both give 100% effort defending and attacking which is brilliant- its which one gives more or less then the other where we need that player-deepish or attacking?I agree with your analysis of Son, much more direct, and as a team we score more goals. I think he'll start with Son. I think Poch does have a strongest MF and strikers, and it really is a 6 pointer.
You can't say a strongest starting XI as the full backs really do seem interchangeable. They need to be with the running the system requires them to do.
I feel we will start with Lamela - same start as watford with changed FBs.