How do online comic marketplaces like eBay or MyComicShop compare to dedicated comic book retailer websites?

Marketplaces like eBay offer vast selection and potential for deals, but often lack standardized grading and reliable seller reputations. Dedicated retailer sites usually have stricter grading, better customer service, but may offer less variety and fewer 'steal' opportunities. MyComicShop combines marketplace and retailer features, offering a balance.