I am PRETTY Sure that ESP/LTD does not make "FULL THICKNESS" models for distribution in the US with the exception of the EC100CTM. However, if you played them both you should be able to tell if they are the same thickness roughly. They both have carved tops, so I dont think they would have much of an issue. Could you further clarify what your prefference is? The 401 and the 256 shouldnt have a different body thickness, so can you clarify what you "prefer"? Hope I can help!
Something like the ec-1000T would be a full thick body with the T denoting 'traditional' (correct me if wrong!?). I want an EC-401 but have seen pics on google images of the back with no extra body cut-out, so more like a regular Les Paul. I was just wondering if there was some documentation somewhere detailing the size differences of differet models? The EC-256 has the cut-out and thin body which I really liked.