Because every single blogger in the world has posted about this, and because you miss important stuff when you watch CLANNAD in SD :

That’s right, even Nagisa can use the Sh****gan.

Ok so this topic has been beaten to death by a rusty hammer. What I can summarize from all the blog posts and all the comments: nothing important was left out. (If you want REAL comparisons all the sites linked above have pretty screencaps showing the difference, the world doesn’t need more).

My personal thoughts? The fact that now I KNOW half the character’s faces are cut off because they can’t fit them in bothers me when I watch it in SD =( That and WS just feels… more spacious… just like how CLANNAD should be. I’ll probably continue to watch the SD first but since CLANNAD is so enjoyable, I’ll probably re-watch in HD as well.