As kain said I found the JC HiFlow to be the most durable with great venting.

The FTW body is very durable with great venting and there's only 2 vents... who wouda thunk it?
But if this is for your Mugen that your thinking of converting... the FTW body is kind of old school narrow and won't fit very well if your going to get out to the max 296mm width.
JC HF fits my Mugen best of any I've tried.

There's also someone selling double thick sc bodies on ebay... my buddy and I have a body being prototyped that is double thick as well. Will see how it goes, mold is done now just having issues pulling the sides down cleanly. May have to go the next step down in thickness but still thicker than all the others.