well Kanon 2002 is more candy like in art work, and Kanon 2006 is a retelling with more scenes and more info, toough it won't hurt you if you watch Kanon 2002 first, both version have something the other doesn't, it's not much and you won't miss out on only watching Kanon 2006 but still it's more preffered if you watched 2002 and then 2006, it's basically the same story told twice, but the latter has more stuff, while the first has a few things the latter doesn't, l recommend it personally but l won't force you, l can't fucking dare to watch it untill december, had to take a year break from re-watching this show, there is one arc that gets me dry, and l need a bucket for it, fuck tissues, l want my BUCKET !