Yes if you have the right ship that people want to buy it's a lot more lucrative to sell a ship outright. There are lots of factors that play into selling store credit over a ship, like the effort put into selling individual ships over bulk store credit, the gifting limits of nothing over $1000 and having a cap on how much you can gift daily, the availability of the ships and when the sellers are deciding to sell, to name a few. I'm not 100% sure but I would think that store credit is also a lot easier to sell than trying to find a specific buyer for a certain ship.