Probably because it sounds like you are using the same settings.
Settings differ from panel to panel between the same product lines. Considering these 2 sets are from different product lines you probably need to calibrate or at least play around with some settings on the VT.
Setting them to have the same exact settings won't work.
Also, as your panel ages it will actually get better in terms of picture quality.
yeah it seems my panel ST30 60" i am using dnice settings at Low panel brightness. I am getting used to a good calibrated picture . mid panel brightness is too high and not correct .. Seems like my tv is getting better , especially at night HD tv was looking really good. I probably got 500 hours on it now