[Jeff Lee]

My take is that JE took TRW pistons and copied them with some design improvements. So if TRW got the valve notches in the right place, then your OK. Unfortunately that is not always true.
CP came along and used factory OEM blueprints. CP found that TRW pistons were sometimes off. Being that P/V clearance is critical, that could be a big deal. And when CP started, they had the latest and greatest ring groove cutting fixtures. I do not know if JE has invested in the latest machinery for that operation but as you know, ring clearance is crucial to performance.
The bottom line, and this is just my opinion, there is a reason why you are seeing a 50% price difference. Ask these questions when you call them back.
You might also call Diamond or even Weisco. I have experience with Diamond but not with Weisco.