Eh, I appreciated Clannad more than Canvas 2 simply because I can play it on fullscreen without issue..
As to the original question, DC:IF didn't feel as sad since I still get the feeling everything will turn up fine. I dunno, whenever Sakura shows up, she kinda has a soothing effect to me (and not just because she's a loli).
Clannad, IMO successfully projects bleakness and hopelessness in those scenes that you end up cursing the world for its cruelty. Fuko doesn't really quite alleviate the sadness, but she'll do as a ninja.
It's the magic factor, I guess. In one, it's prevalent while on the other, it barely shows.
With that, you'd know which one can easily be resolved. That's my opinion though, feel free to disagree.