In my personal opinion, you're better to get an HP, especially if you intend to travel, since the continent-wide DB is included in the radio. The benefits of the HP1 (large color display, automatic recording, database included, various utilities like Discovery Mode and Trunking Analyzers) far outweigh the negatives (larger size, not usable as a belt-clip radio) for me.
It doesn't much matter any more where you're going to use the radio, instead what you're going to do with it. If you intend to carry it around in a portable fashion, the HP1 may not be your cup of tea, because it's not exactly a hand-portable design (though it would be possible to use it as such - just not without being cumbersome). If you want to mess around discovering new frequencies and analyzing the data coming off a trunk system, the HP1 really has no rival IMO at the moment.
Both of them do the GPS switching of systems/zones quite well, with the same equipment right up to what you plug into the scanner. Even on a 50 mile trip, you will appreciate the scanner automatically adding and dropping systems/groups while you're on the move.
Basically as far as I'm concerned, the only thing that would make the HP1 unsuitable right now is the need to have a truly portable radio you can carry around in a pocket or on a belt.
