The Pro-106 uses a design created more than a dozen years ago, whereas the 436HP was introduced in 2014.
While the 106 is more sensitive, hearing faint signals, it's also much more prone to overload and desense due to strong nearby transmitters. Nearby cell towers seriously affect the Pro-106. Although I'm surrounded by a forest of cell sites, the 436HP is unaffected.
The Pro-106 has a limit on the volume of frequencies and systems that can be programmed. While the V-folders are available, they only allow a different programming scheme. You're still limited as to what can monitored. With the 436HP, as well as the other HP series scanners, you can program a much larger number of systems, and monitor most any combination at one time.
If the OP does much traveling, the database on the memory card, and the use of a GPS, greatly enhances the ease of setting the scanner up for a trip. Also, if that trip, whether for business, vacation, or visiting friends or relatives, passes to or through a major urban area, the odds of running into a P25 Phase II system are nearly a certainty. The 106 cannot handle Phase II, whereas, the 436 can, and with the optional upgrades, can also deal with DMR and NXDN.