unless you have been selling for a long time and have a popular style or large following, I'd say go with bidding for a start. BIN costs more and its sortof a waste for the low prices ACEO's mostly sell for. You can do both also...a low starting bid and a BIN to see how that goes...the only way to tell is to send out some feelers to see which works best for you. Try a couple with just bids and try some with bids & BIN. Either way, if it's not hugely popular or seasonal like a christmas or hanukkah image, then a BIN in my opinion is not necessary.