Due to the ability of players to search for a specific item and then have the ward the retainer is located in, there is no specific ward that sells faster. It's all just about the price. People will go for the cheapest one regardless of which ward it's located in. The only thing that does matter is the "tax" or "surcharge" a ward charges the seller for each item sold. You may sell an oak log for 100 gil in the woodcutters ward and get 95 gil back after a 5 gil tax. If you sell another oak log in the menders ward, you may only get 85 gil back due to having a larger tax due to not being sold in the "correct" ward. This difference in tax was a way to encourage people to sell items that are pertinent to the ward the retainer is currently in.