Good question - I'm interested to know which is the better option as a buyer too.
I was previously looking at a Tudor that was advertised by a pawnbrokers on both eBay and Chrono24. Their store was nearby and I asked if they would prefer me to go directly to the shop or through eBay. They were happy for me to visit the store an inspect but they said they preferred to keep transactions on ebay...I couldn't work out why. Also, I was under the impression Chrono24 took a commission whether you sold through the site or not.