Samu hits far better crosses, corners and passes, has superior vision and is less likely to lose the ball in a stupid manner.
Alexis is less inclined to cut in with the ball at his feet, but more likely to make off ball runs into the box - this has helped in certain transitions to attack and overwhelmed opponents.
He's also less likely to avoid physical battles, as someone else mentioned.
Both are hardworking, energetic, comfortable with midfield duties and far better RW/RM options than Paq.
However Samu is the clear choice for now. There's more end product and self-awareness.
None of them are dependable goalscorers, but Samu has a big advantage as a left-footed player on the right flank.
I can't see Alexis score, without GK howlers or dummies that confuse the keeper.