Is there a big difference between DVD and HD DVD?

[AbyssKiller]

I plan on buying the Transformers movie. But I don't know which one to buy.

I only have my PS2 to play DVDs and watch it on my TV. WHile HD DVD can only be played on my computer and I don't really like to watch movies on it, mostly because my ****** don't like to watch in a small screen.

I was wondering if there a big/significant difference to make me buy the HD DVD over the normal DVD.

I remember buying Pirates and watched the HD DVD and didn't see a difference.