Pardon me for my ignorance, but would I load songs just as I would an mp3 player? I’ve learned that assumptions are rarely qualified.
Exactly like the MP3 player ... you'd use iTunes.
Now, depending upon how 'new' your Apple product is (ie. iOS 5) you may be able to wire-lessly update or change your song list. Just open iTunes and select the songs you want on the device, and the device will find and synch with your computer over your Wi-Fi network - all by itself. I do this overnight, because (in all fairness) I have found that a wired synch is much faster thant he wireless synch).
The correct answer is, of course, what's best for YOU. Otherwise, "best" has no good definition. The iPod Classic is on the way out. Get it only if you must have all your huge music collection with you at all times. The Nano is good, but memory is limited, you'll only carry a subset of music at a time, depending on the size of your library (16 GB is thousands of songs). But then also forget the Zune, it's been discontinued as a market failure. There are others out there though.
And of course, how will you use it? These touch-screen devices aren't as good to use eyes-free. With the old click-wheel you could feel your way around the interface. If that's important, get a previous-generation Nano used, really cheap.
But my answer is to wait. Apple will likely update their iPod line within the next month or so. That will change the equation regardless of what you end up buying.