X-heads vs J-heads: what's the difference??

i would much rather recommend a set of 308 heads..better chambers and better intake and exhaust ports...better head..unless you cant use the smaller cumbustion chamber ...
out flow x heads..
the biggest draw back it they often prone to cracking in the area between the intake and exhaust seat..
saying this im running a set of J's with offset intake pushrods and heavily modified short turn walls on the intake.
i would have done it to a set of 308 if i could find a set that wasnt cracked.
cheapst