My two cents.
I just bought the PSR500. And I NOT getting rid of eithor the 996T or the 396T. I love the programming philosphy of GRE and it works well. And as preformance goes, well they both work well where I'm at in the Phoenix area-I do not carry around thousands of dollars of test equipment to nit pick with. Having said that, I am using the PSR500 to control the 396T using Pro96com-which is an interesting ultility.
But but but, for mobiling and for mobiling the distances I do as a trucker, I still say that the Quick-keys of Uniden are better then the V-folders of GRE.
Both GRE and Uniden are high quality units and one can't go wrong with ithor in my opinion. Really depends on you and your tastes and what system of programing you want to learn (I am comfortable of both worlds).
I am going to enjoy the best of both worlds and will no doubt use my PSR500 as often as I use the other, especially in situations where they work together.