First off, aside from the 44 gold for rank 8, the recast itself only costs 1.8k ec for the entire set reshape, which, at 150, is going to be pocket change.
I prefer rank 8 over Dragon simply because of the Attack and Defence levels as a set bonus, and on the weapon, which are indispensable.
While Dragon's static stats are nice, there are simply some things that I'd prefer over dragon, such as the 10% pdef and the like.
Honestly, it's up to you, but with time and patience, r8 can overshadow dragon for a lot of classes.