That all depends on what you plan on monitoring? If conventional (analog or Project-25) are big in your area on VHF/UHF; I'd say go with the Uniden BCD996XT, with the addition of a GPS unit, it works out really nice when travelling around because it can enable and disable groups via GPS location. That said, if Project-25 trunking is big in you're area, the PSR-600 has much better multi-site tracking capabilities; it's not 100% perfect, but it does a little better than the Uniden in this respect; however, the Uniden is an all-around much better unit for search ranges, conventional scanning, and just the amount you can program into a single profile without the need for constant reloading, etc.
I have them both and I like them for varying reasons; if it were me, in my car, and you have GPS functionalitym you can't beat the Uniden BCD996XT...
I don't have either scanner,but between those two scanners I would choose the Uniden Bearcat BCD996XT because of its features and that I like Uniden.Am not to sure on the GRE PSR-600 because I have heard that it has overload issues.
I have them both also. 996xt is going in the vehicle permanently and the PSR 600 will stay as fixed unit. Tried them both as a mobile and the 996xt wins mobile for myself. Scan list usage and RF characteristics/RFI rejection make it winner in the mobile. That said I agree with with W2GLD, if multi-site trunking is your primary scanning target the GRE may be a better choice.
The PSR-600 is more sensitive so it belongs in the car,it also has signal stalker for finding frequencies that are analog and P25 without knowing the full info for that particular digital channel you found.
I love my 996xt as well it is lot more SELECTIVE for a base installation,so I keep my 996xt in the house to ignore intermod.The 996xt in my opinion has better BUTEL software and is easier or better in the house.
They are both LOUD!
They both receive well.
They both have a close call feature.
They both come with DIN sleeves for mounting in the car,knobs and a bracket.
If you want a remote head ,go with the 996xt ,the radio shack will only go in the dash or a jotto desk.
They both do the same thing but the radio shack receives better for air band.
Hope this helps.