For me, it depends on whichever lift I happen to be emphasizing. There have been times when I'm strong on incline and suck on flat and vice versa. When I first started lifting, declines outwieghed my incline and flat lifts by 50lbs or more. Today my declines suck by comparison because I don't do them much anymore.
Same thing with DBs. I used to think bar was easier until I started doing DBs exclusively. Now I can do proportionally more on DBs than with bar.
So barring injuries or known muscle weaknesses, I don't think one is inherently easier than another.