I think GR has some better songs than anything on Watershed, but Watershed does not have The Grand Conjuration, so it's automatically better.
I still think TGC is a great song and an important one on Ghost Reveries; while it may seem a tad to long, it's a killer track right after hours of wealth and it fits there because it's so heavy.
Porcelain Heart on the other hand (and on the other album) fails to impress me somehow and bores me a lot more because it seems way too simple and also the chord progression in the "ahhaahaaah"-part is not too interesting.
TGC has this evil vibe that I miss on most songs on Watershed anyway.