I'm not really sure if it's better. Both have their positives. S2 is more complete as a mobile device I think, but Galaxy Nexus comes with stock ICS and a bigger screen.
I'm looking forward to Galaxy S2 but..hoping that it won't be bigger, faster etc etc.
I hope thel'll go the "innovative way" - thinner, "smaller", cooler etc. Or that there'll be some other device like that.
A company coming up with a device with a really small bezel around the screen (with screen taking almost the whole front panel, ICS allows that because of no physical buttons) that would be thin and with acceptable hardware (for example a 4 inch screen, 1ghz processor, a good camera) - they would have my money.