Really it's more subjective than that, and each system seems to work or not work on Uniden or GRE or both or none. Up until the x36's came out, NOTHING worked well on our DTRS. The closest to decent reception you could get was a PRO-106 with the 800MHz antenna, and even then it was hit or miss. With the 436, I'm able to decode most (at least 95% or higher) of the transmission on that system. It was a breakthru for us here in Phoenix - I had all but given up on listening to this system prior to that.
Also, my previous experience with GRE products was that they were not as sturdy as the Uniden models. I had a PRO-96 that literally fell apart from a few years of normal use. Now, I admit I'm rough on scanners, but even so I've got plenty of old Unidens - older than my now dead Pro-96 - that still work just fine. So it depends really on the model and in some cases, the systems being monitored when trying to determine the best scanner for you.
-AZ