I recently purchased the 396XT. I do not have or have never operated the PSR 500. I have had many scanners in life, to include the BC246T, Pro-96 digital..ect...
The following information was taken from
Uniden Bearcat BCD396XT Police Scanner Radio
The GRE is better IF these are most important to you:
* Better digital decoding, especially on simulcast systems.
* You prefer a larger radio with better audio.
* If you prefer separate volume and squelch controls.
* If you don’t want or need the extra features of the BCD396XT
* If you are not bothered by excessive strong-signal interference.
* If you need higher sensitivity.
* You like to have Virtual Scanners available to you.
You will want the BCD396XT IF these are more important:
* You prefer a smaller, compact radio.
* You prefer a more solidly built radio.
* You prefer a simpler but more detailed display.
* If you want the amazing feature-set of the BCD396XT
* You prefer the Banks/Systems/Groups method of programming.
* You need or want the GPS features.
* You will use the radio in a high interference area.
* You want to have a lot of channels available all the time.
* When fire tone-out capability is important.
* You monitor a large networked system with multiple sites.
Based on having the BCD396XT, I discovered that it provides exceptional audio for being a small radio. It appears to decode APCO25 just as well as any of my other scanners. It is full of features that make the scanner unique. The 7 backlight features can be customized to each channel and can have a fast flashing lights option for each assgned channel as well. Several Alert Tones can be assigned to each channel.
On the other hand, I found it more difficult to program, without the assistance of software. But, the more time I spend "playing" with it, it is getting easier to understand how it is programmed by hand.
I hope this gives a little insight in making your decision. Good luck!