Flat Panel Hdtv

With All Other Aspects Being About The Same Except Price, I Was Trying To Compare A 40" Sony Flat Panel To A Sony LCD Of The Same Dimensions. Which One Has A Better Picture Or Some Quality That Makes It Noticeably Better Than The Other? Due To Not Presently Being Able To View Them Side By Side In A Store, I Am Trying To Compare What I Can Via Online Shopping. Your Response Doesn't Have To Address Sony Brand, But Rather HDTV Flat Panel To HDTV LCD. Thanks.