I don't personally have experience with Adbrite, but have heard in general the CPC is lower than Adsense. The good part is they have a much lower payout threshold than Adsenses $100 minimum earnings.

The best option would be to test both out and see what one performs better with your site in particular.

AdBrite ads tend to go on sites that might be frowned upon by AdSense. I would stick with AdSense and find out other ways you can monetise the traffic.