If you want to compare Willock to anyone in order to caution against selling it's definitely Ramsey. They share many of the same strengths and weaknesses. Willock probably isn't quite as instinctively brilliant, but he's got more power and seemingly won't spend half of every season injured.
I'd definitely keep for now, we've got a long list of undesirables in the squad that we can sell and midfield is one area we're not going to be stacked.