For Jack there are pro's and con's on both options. AFC are very much a club on the up. He is playing under a talented manager who see's him as the keystone to the team. Most of the squad are tied up on deals with one of the spfl team of the year players joining said squad in a months time. I also think he's canny enough to realise that another year at Aberdeen where he's playing every match would be no bad thing for his development.
I'm not saying he's not ready to go, he's good enough no question, but, at 23, he can't afford to be sitting on a bench week in week out. He needs to go to a club where he will get plenty game time. Jack is one of the best cm's in the league but for the kind of clubs being discussed he needs to be the best cm in the league to have a decent chance at regular game time. Probably what's best for all parties (with say an everton size club if one were to bid) concerned would be to reach a good price for him then to get him back on loan for next season for no fee. Lets face it, there is no danger he is sticking around for anything longer than a year. This would ensure a fee, keep the player an extra season (hopefully at little cost), the player is happy his career is going in the right direction and the other club is happy that it's player is being given more development time in a positive environment with the prospect of getting a better player than they have paid for.