What a wonderful world Panasonic owners live in.
The folks, who want the best when watching movies, Blu-ray or DVD, during evening hours, and are not critical about what they watch during daylight hours, can buy the ST50 series of displays. These same lucky folks may also have no interest in using Internet connectivity as part of their entertainment options. For a much reduced price they can enjoy picture quality that is so close to the higher end models that it might take a professional calibrator to notice the difference.
If people are very interested in adding Internet material in their home entertainment, they can probably get much improved performance by moving up to the GT50 line. At the same time they can probably improve their day time viewing quality, and for many, they get an improved appearance with a more attractive bezel.
If someone is very much into the appearance of any large black device that they put into their home, and they also want the very best in black levels, they can move up to the VT50.
To top it off, anyone who wants the very best industry standards performance from any of Panasonic's "50" series displays, they can engage the services of one of the excellent professional calibrators that are active here at AVS. (See the links in the signature area at the bottom of my post.)
If I've missed some critical characteristic of the ST, GT, or VT series displays that you think is critical, I apologize. Enjoy.