With the cost of quality cotton fabrics these days I would keep everything I loved and thought I would use someday. Having to go and repurchase might become costly for you especially if you already have all the fabrics you would need to complete any type of project. Selling the ones you aren't crazy about makes good sense.
Offering what you won't use here is a great idea. A bit more trouble than a personal sale but many quilters here would appreciate your fabrics.
Whatever you decide is best for you, I wish you much luck and know you will have made many people very happy.