I think he's a better RB while Dest is probably better as a RWB but both could be useful and having a true competition between two youngsters for a spot in the team would be nice to see as well (since we're not really used to that).
I really hope he'll be given a chance but we'll probably sell him and keep Roberto as a utility guy alongside Mingueza. Hopefully Emerson will at least get a preseason to convince Koeman before we sell him though.
OTOH if Koeman will continue to play with 3 ATB we could also try and convert Emerson into a CB like JamDav suggested. I like Mingueza but think Emerson has more potential and could be better in that versatile RB/CB role longterm if he wouldn't establish himself as our starting RB.
I'm all for letting him and Dest fight for the RB spot. They're different types of players and while one or the other isn't clearly better, it'll be a good option to have for the coach depending on approach.
And besides, IIRC Betis get 50% of the transfer fee. We paid 6m each for him, meaning a 20m transfer won't give us a lot of profit.
It doesn't hurt to try him, unless we get a super offer.
It's even more complicated than that. There's 3M in interest that Barca would need to add to the 6M to retain the player (9M, 15M in total) - even then, selling on this summer Betis would still get 50% of fee but after this summer only 20% sell on fee
It would mean that if he were to be sold this summer, it'd have to be >=30M in order to cover the costs of a player who has not yet played a minute for Barca - anything less would be a loss. Nevertheless, 9M would need to be paid this summer, unless Firpo enters into the operation to go back