I think I asked tester about these (or similar) a while back and got a resounding "wouldn't touch them with a bargepole", suggesting ceramic bearings of unknown provenance and likely cheap/poor quality are almost certainly worse than regular bearings from a known brand.
J&L stuff generally decent quality right? Looking at one of these, mostly because its the cheapest GXP bb I've found
http://www.ebay.co.uk/itm/J-L-BSA-68mm-Ceramic-Bearing-Bottom-Bracket-BB-fit-SRAM-GXP-Raceface-Shimano-FSA-/302250201067
Will ceramic wear out faster than steel bearings? I don't care about watts