You'll see more contrast on the LG. The Sony's screen is larger, and that is something you will notice. I have a 42" and a 40" and I can easily tell the difference. There are more ports on the Sony, but that really depends on what you'll be hooking up to it. There is a difference between regular av component input and HD av component input.
I have an LG. I love it. The picture is wonderful and the sound is great. I personally don't care for Sony TV's, their picture quality has never impressed me. If you can, try to look at them side by side in a store. That will give you your best comparison.