They were having this debate on the Aston Villa board of all places the other day, so I thought we should have it too. (Heroes was winning there - but I should point out a lot of people got over-aerated about Celebrations because they were boycotting Nestle. Red faces all round when I pointed out Mars made them!)
Anyway, my vote narrowly goes to Heroes. I love Celebrations too, but they do have the dreaded Bounty in them, so I end up throwing them away, whereas with Heroes I like everything.