The cairn on Foel Fras has almost merged into the surrounding rocks though, so I still wouldn't entirely discount it.

I know what you mean about Crib Goch (if I ever get there), from the point of view of intensity of experience anyway, but from the two biggest Glyderau you are surrounded by the full picture, sandwiched between Carneddau and Snowdon ranges, Tryfan, etc. From Crib Goch, if you can bear to look around, views are largely blocked by bigger ridges. From Glyder Fawr, you get the lot on a clear day.