I've been looking at these two models for a good month now. Originally the price on the Sony was a bit too rich for my blood but now I can get them both for the same price. I also looked at the Samsung LN-T5281F but its currently going for $1200 more.
I've done lots of checking and I think overall the Sony has a better picture quality. Also for some reason everyone I have asked so far said they would take the Sony at the same price.
I checked out consumers reports and the XBR4 is ranked at #1. So for me the jury has weighed in. I'm going out to get the XBR4 in the morning.
I'll let you know how it looks.