Which would be the better choice if I had to manually enter frequencies, the HP-2 or BCD436HP.
If you want to manually enter frequencies, directly on the scanner, you can do that on the 436HP. It can also be done on the HP-2, but only if you purchased and activated the Extreme Upgrade, which is an extra cost option. However, even without the Extreme, you can manually add frequencies to the Favorites lists on the HP-2 via the Sentinel software on your pc, then upload the revised list to the scanner.