No real easy answer to that question. Many times the answer is neither . Unless you have HIGH valued extreme rarities , auction houses can be the absolute wrong place to put your coins. Many dealers myself included Buy a good majority of coins FROM auctions . In fact before the pandemic hit most material IN auction went TO dealers . You can try selling them yourself online , many people do with varying degrees of success from an occasional seller to some like myself who make a living at it . Where to sell is really dependent on the kind of material and the demand there is for it , and how quickly or not you need the funds . One other issue sellers have to consider in addition to associated costs of selling a collection or accumulation of coins , the implication of taxation . This is a major issue if a high value collection is disposed of . That in itself is or can be a HUGE issue .