I have both the 536HP (as well as the handheld 436HP), also both versions of the Home Patrol (HP-1 & HP-2).
Both the 536 and either version of the Home Patrol use Favorites lists for programming, and have the RadioReference database plus the Favorites lists loaded on memory cards. The database for either series is updated weekly, both use a variant of the Sentinel software, and can be paired with a GPS to load systems in range when traveling.
The Home Patrols are good listening scanners, but you don't have the control options and features that are present on the 536. The HP-1 & HP-2 have a much larger, and more readable (IMO) color display. The Home Patrol 2 will track P25 Phase II systems, as does the 536HP. The HP-1 is only P25 Phase I compatible.
With the 536, you have Close Call, just like your 396 or 996. You also have Priority scan available, if so desired. Unlike the HP-1 & HP-2, the 536 also has quick keys, so that you can easily turn not only Systems on and off (like your 396/996), but also the Favorites list(s), and Departments (which are the equivalent of the Groups you are familiar with in your current scanners).
The 536HP also has a true narrowband filter, and many report it works better on simulcast systems than their Home Patrol scanners. Also, the 536 has the alert LED feature, so that you can color code various channels by Service Type if so desired.
I have not had problems with my 536HP, unlike the complaints you may have read. Mine was included in the Headphone recall, but that was taken care of in a reasonable amount of time. You may want to check with someone in your area, to see if either model works significantly better than the other.