As it stands both players have their attributes, but I wouldn't say what I've heard of Rashford is all hype. Having seen him play, he's lightening fast, cool under pressure, can play wide, through the middle and has a bit of skill about him too.
When Kelechi replaced Kun on Saturday, he dropped deeper than usual and showed a level of skill above what I've been used to seeing from him and he looked like a proper play maker doing so. Both Rashford and Kelechi are young, brilliant for their age and have room and time to improve. Both clubs look to have potential starts on their hands.
As for Kelechi's limited game time, it's baffled all of us why Bony has been selected ahead of him until very recently. Also with Aguero's injury record, I keep shitting myself that he'll pick up another injury whilst Manuel keeps playing him until the death in games that are already won and under our control. Many times I and many have wondered why risk Aguero until 5 minutes before the end of a game before Kelechi is brought on to get no meaningful game time.
Perhaps Kelechi's advancement is no longer a concern for a manager who won't benefit from it, as I can't think of any other rational explanation.