If you do a lot of collecting, a proper handheld GPS is worth the small investment.
I have an iphone 4, and there is nothing it can do that compares to my GPS.
In terms of form, hiking GPS's are meant to be dropped, are waterproof, and can be used with gloves if designed well.
In terms of function, a good GPS works under tree cover and will take you within 1m of your waypoint. 10m might seem pretty good, but in the areas I collect in everything looks the same and it can be hard to find a tree you last saw a year ago, even knowing it is "somewhere around here".
That being said, do some research and you will likely find that the Garmin GPSmap 60CSx is the most widely recommended model. It is an old design, but still probably the most popular GPS out there - and for good reason. The interface is dead simple, it is tough as a brick, and it is insanely good at locking onto satellites even under heavy tree cover. Also, the screen is easy to read in bright sun. Don't let the old school graphics fool you - it rocks. As far as I know they are still making them, almost 10 years after they were first released.
When I was looking for a GPS I bought a new model Oregon, a new model Colorado (touchscreen), and and older 60CSx at about half the price. After testing them for a few days, I kept the 60CSx. It is just better! Touch screen GPS's are annoying to use, especially with gloves, and can be practically impossible to read in daylight. And the Colorado and Oregon did not work nearly as well under tree cover. Not to mention that the 60CSx just felt way more solid and better built.
Go with what works!
Hope that helps... you can probably tell that I love my 60CSx.
