You have to pick:

I think with the islands you'd have a lot of individual kingdoms with diverse culture, whereas the supercontintent would lead to mega-empires and uniformity.

I suspect science would be less advanced is the island scenario, partly because of small groups who don't co-operate and partly because of the constant rebuilding from ocean storms.

There would be a lot of desert on the supercontinent though.

Ah, screw it. A world made up of millions of islands is just cooler. I don't care about the other ramifications. :P

I think the island continent version might be more advanced overall, actually. Diversity can be good for technological progress - lots of competition, lots of places for ideas to be tried in new ways. And I think the world's ecology would be much more productive (there'd be almost no desert) so it could support more people in total. Great Britain is about 1/700th of the world's land area, and Great Britain was able to conquer a vast empire and get the Industrial Revolution going so it's a decent enough size for a civilization.

I go with the supercontinent. Goodbye Navy, hello massive-scale infantry invasions! FOR THE MOTHERLAND!

if its all one super continent, wheres the water? looks like we're all dead from dehydration