Edited the OP as best I could.
I and outlawauron have both betas, and we both agree that Killzone 2 is quite the superior game.
The game is so damn polished already, and I can't wait to see what it's like in four months.
Edit:
And I also believe that Killzone 2's story will be really good. The histories on Killzone.com are really in-depth, and are really cool. They show just how interesting the Killzone Universe is:
http://www.killzone.com/kz/news.psml?kz_news_article=The+First+Extrasolar+War&kz_news_page=0
This, combined with the fact that the guys behind Heavenly Sword's cutscenes are also working on Killzone 2 lead me to believe that it will be one hell of a story.