There are two different varietals of jackfruit: one with firm/crunchy flesh (this is the kind you see canned in stores) and the other with creamy. Durian is like the jackfruit with the creamy flesh (in texture), but durian's fruit is larger. They have a similar mouthfeel (and taste: to me, that is), but the smell puts off a lot of people. Unfortunately you don't get the creamy jackfruit in a lot of places so you have to hunt for it. Luckily my parents have a tree in their back yard....

Based on looking up durian in Wikipedia, and having seen large jackfruits in India, I can say that jackfruit can grow much larger.

Can jackfruit be eaten raw too?

Yes. The seeds can also be saved and cooked. And if you have the young fruit, you could cook it in say a curry like a meat substitute.

Is the creamy jackfruit the same thing as cempedak?

Jackfruit flesh is firm and juicy. In contrast, durian flesh is creamy -- imagine thick, dense whipped cream around a jackfruit-like seed.

You can't cook with durian seeds like you can with jackfruit seeds (i.e. chakkakuru upperi or chakkakuru mezhukkupuratti)

I was wondering the same, as someone who has eaten jackfruit but never durian.