I currently own a Nexus S, and am due for upgrade in 2 weeks.
I was originally torn between the G Note, GS3 and G Nexus. The fact that the GS3 does have handwriting recognition was enough to knock the note out of contention for me. Although I do like the size, and I do like the S-Pen, I just won't make the use of it. It is a pity that the Wacom digitizer didn't make it into the GS3.
So now it is between the GS3 and the G Nexus. And this is where I am torn.
I have never been a fan of TouchWiz, although the reviews of the GS3 says Samsung have gone a long way in trying to sort this out. So I am less worried about TW now.
Moving on to the core OS - the G Nexus is due to receive Jellybean soon, but is it? I am a little bit wary considering the hash that was made of the OTA update of ICS to the Nexus S, receiving it well after the G Nexus was released with it as stock. In fact, not long after my Nexus S updated to ICS, so did my bro's HTC. So was there any real benefit? And how long before the next Nexus phone, there must be one due soon.
The S3 definitely has the better tech, and will most likely get JB eventually. So that is what I am leaning too - but I am still undecided.