I found my first 800+ caches with my iPhone 3G and tbh, wouldn't have a bad thing to say about it. At Christmas I got an eTrex Legend HCx, and it's been a revelation! It doesn't have all the bells and whistles of the more expensive units, but it sure gets you to GZ with less drama than the iPhone. Later iPhones may be better, but in my experience I typically overshot a cache by 20m, then 10m past in the other direction, and so on until the blue dot eventually settled in roughly the right area. With the eTrex (and I imagine most decent GPSr's), you just count down: 20m, 10m, 5m, 4, 3, 2, 1, cache!
I still use the iPhone for accessing cache description, hints, etc. and posting field notes, and the satellite photography comes in handy at times. Can't comment on the Dakota I'm afraid, but I'm now a huge fan of the eTrex. Like any new piece of kit, it will take a little getting used to, but I doubt that you'll regret it. I use free OSM maps, which are great for my normal tramping grounds, and GSAK to manage everything on the PC. You need a little techie know-how to get it all set up, but there's plenty of help out there.
Good luck!