Should I buy the Harry Potter Ultimate Editions in Blue-ray or regular?

I'm a huge Harry Potter fan and I don't own all the DVDs because I knew they were one day going to come out with something awesome like the Ultimate editions. My only dilemma is whether to get them in regular or blu-ray. What's so great about blu-ray? Is it really that great or will I regret getting them in blu-ray later? I have a PS3 so I can play them...but what are the pros and cons of getting blu-ray?
If I should just get the regular DVD, why?
Thanks in advance!