This is an interesting thread on ebay.

Personally, I think that there are some factors that people weight differently in choosing a venue:

fees: how much does it cost?
sales: how much can you sell?
traffic: how many people come to the site per day?
cachet: does it sound cool to people?
community: are the other sellers nice?
customer service: is it good?
bugginess: does the site work?

Personally, I'd prefer high fees, high traffic, and high sales to low fees, low traffic, and low sales. Cachet, community and consumer service are less important concerns. I dislike a buggy site.

I think that if you need the money, go with the high sales even if there are high fees. If you can afford to wait for months to get a sale, you can go on other venues.