I'd rather back Poch to finish the job with Onomah. In 12 months time I think Onomah will have eclipsed Barkley.
Barkley has a fundamental lack of a footballing brain, which will keep him as a bottom half EPL/upper championship player, like David Dunn before him.
I've yet to see anything in Onomah which suggests he'll make it as a PL player. He's made a reasonable number of appearances now, albeit a lot as short cameos towards the end of games, and he's yet to make an impact in any.
I'd have liked to think he would at least have shown what main skill/attribute he has which could give him the chance of making it - yet he's not shown, for example, that he's able to beat a man, or play a defence splitting pass, or have amazing skill, or pace, or....and to make it worse, he just saunters around.
To say that he will be better than Barkley in 12 months' time is just ignoring all evidence so far