Remember this. Whistler did not buy the proprietary rights for radio systems like Uniden. Therefore, a Whistler won't successfully "track" conversations on DMR or NXDN. Furthermore, if you have ProVoice in your area, you can forget that with Whistler. It seems as though Texas has a noticeable amount of ProVoice systems as opposed to the rest of the country. I don't know if Whistler has a GPS function either.
Whistler does not have a GPS option. That is a Uniden only feature.
While you can scan by location, based on your zip code in any of the database scanners from either manufacturer, Uniden & Whistler handle this differently. In the the Uniden scanners, you can specify a location via zip code, GPS, or entering actual latitude/longitude. The scanner then will load channels and systems to scan based on the service types you indicate, your location, and a range. (For a more complete explanation of Range, see this
article.) For the Whistler scanners, your location (via zip code) is used to load systems in the county that the zip code maps to. If you are near the border of the county, it would not load systems/frequencies from neighboring counties, only from your 'home' county.