I have no experience with any of the mentioned scanners other than the HP-1. My best advice is to take the time to consider a few things. What features are important to you?
If you buy a desktop unit like the BCD996XT or BC536HP...will you regret not getting a hand held (BCD396XT or BC4365HP) that you can take on a quick trip to the store? Do you want the ability to listen to P25 Phase 2 IF any nearby counties would switch (which I don't think is likely within the next few years)? PA is in the talking stages of replacing the PA STARNet (Open Sky) radio system with a Phase 2 system, but that is years away. If so, you need either the 436 or 536.
If you want a scanner you can use as a base, but also take along in the car, the HP-1 might be a consideration. I got mine MAINLY for use in my vehicle, but I often hook it up as a base on the weekends. Decide which one you want and then price it out. I think that is how you get your best deal.