My biggest use for it would be geocaching, second mapping
Go for the 450 Dave. It has stuff built into it for geocaching. Once you understand how the map stuff works, it's easy as can be.
From Garmin's site.
"Oregon 450 supports Geocaching.com GPX files for downloading geocaches and details straight to your unit. By going paperless, you're not only helping the environment but also improving efficiency. Oregon stores and displays key information, including location, terrain, difficulty, hints and descriptions, which means no more manually entering coordinates and paper print outs! Simply upload the GPX file to your unit and start hunting for caches. Show off photos of your excursions with Oregon’s picture viewer."