Im going with the 50inch Hitachi as far as spec wise.The picture is really nice on both of them.Sony has a truer-to-life picture and the Hitachi has a clearer picture.Also the Hitachi has a diffusion screen which is nice for a well lit room.The thing that set me over the edge is the Hitachi has 2 HDMI.
I chose the Sony because it was the biggest screen I could fit in my entertainment center and I liked the picture better than the DLP's. I have 3/8 inch clearance on each side. Couldn't get much closer than that.
As a Hitachi owner I am most familiar and happy with their sets, particularly with their ease of use. But I believe the Sonys are great TVs and you will scarcely go wrong with them, either.