I've sold a few things on eCrater. Never on Bonanzle though. I listed both items on the two sites at the same time but they always sold on eCrater. eCrater has no fees which is great. Also, it is mainly TPFers who use eCrater to make a first attempt at selling their unwanted bags. eBay as always is a last resort since they take a huge cut of the profit with their fees and Paypal.
I've had no success on eCrater, though I've sold on BoNaNZa. I wonder what it takes to make a sale over there, given the different environment. I have listed several bags, and at good prices, with good photos, and nothing.
I have sold on eCrater and had very good luck with it. I was able to sell things at what I my net would have been with ebay, so much lower cost to buyer as well. Can't hurt to list your things as it is of no cost!