I like them both. I would say Jadzia was a better character (although Ezri did only have 1 season to develop) but Ezri seemed more friendly (and was hotter). If I had to be friends with only one, I would go Ezri, she seems more my style of fun, and less Klingon obsessed.
Ezri was cute. . . but I was bitter at the change. I still prefer Jadzia. She was a better character overall.
Most times, I tend to agree with you. Ezri was only there for S7, though. If she'd been around as much as Jadzia, had as much character building, I'd probably favor here. But, she was a short-lived character, and it kinda feels like she was a throwaway at the end of it all. So, Jadzia wins just because she was there longer. Extend DS9 out so that Ezri gets six seasons... and it'd probably be a different story.
Jadzia was a Mary Sue, so I hate her. Then they overcompensated for the Mary Sueness by making Ezri so Green and incompetent, that I doubt she would have ever made it past Starfleet's boot camp equivalent.