Funny you ask that. I just sort of explained that in this other
post.
The real reason to use CBR coils is because of cost. I have no idea how much the AEM pencil coils cost, but I always figured they were something like $200 for a set of four. Maybe someone can correct me there.
You can buy CBR coils on eBay used (I got mine in like new condition from a 2008 bike with wiring harness) all day long for $50 for all four.
That's the main reason.
That's actually the main reason I do anything off the beaten path that I do. It's to save money. Or at least attempt to save money. Without cutting corners.
I'm actually convinced they are the same exact coils all made by Denso.