I would say the Sony, just due to the fact that none of the three 46" inchers I got from Samsung worked properly out of the box. HDMI issues, clouds, flashlights, and unresponsive customer service. Heck, just during my 50+ days with those sets, there were countless firmware upgrades, none of which worked. Samsung is king of firmware due to the fact they rush the products to market, and let us be the beta tester. I finally got sick of the headaches of the Sammy 3 thousand dollar strobe light and tried the XBR4. Best decision I have ever made. It works perfectly out of the box, and has not a single flashlight or cloud. The HDMI ports work (all of them), and never ever have gotten a single flash. The build quality is much more solid on the Sony too. The glossy screen of the Sammy was not much of an issue as some have claimed. After owning both tvs for approximately 2 months, I can honestly say the only thing I preferred on the Sammy was the signal strenght indicator, and the menus are easier to use until you are acclimated to the Sony.
I know some have experienced the smear of the XBR, but my set does not exhibit this trait whatsoever. I have tried repetitively to replicate it and have been unable to do so. Don't let a few bad apples sway your purchasing decisions.