The problem with that is we can actually say when Fusion will become available. Heck ITER just formalised the location for their first energy producing fusion power plant. Within the next decade or two you will see fusion being used.
Unified Theory however is still just theory. They can't even prove that it is unified yet let alone work it to do anything. IF it proves true then you are probably right. That MIGHT make a better engine. But quite simply we can't tell anything about it atm. How efficient will the conVersions be? Theory might say 100% but how will that work out in reality? Cost effectiveness for such an engine?
For unified theory there are tons of questions that have no answers right now. Given enough time and assuming that the theory pans out they could indeed be the engines of the future.
Given what is available now and what is known now and what will work now I would have to make an argument for fission and fusion engines over any theoretically possible one using Unified Energy Theory.
Edit: And you would still have to generate the initial energy you are converting into another... Fusion anyone?
[ December 04, 2003, 15:14: Message edited by: Cyrien ]