There are two real advantages - more command prompt access to applications, which allows you to avoid the mouse and GUI interaction in general, and a better selection of code editors.
vi, one of the more popular text editors, in particular I find speeds up my work, but I strongly advise against asking for the relative merits of different editors - it's a sore point and is liable to start a flame war. The other editor with a significant following is Emacs.
Both of these do have a very steep learning curve, but with the amount of software available these days on linux, if you're having trouble, you can always find something a bit closer to home. For a while while getting used to the system I used Geany, which is more of an IDE than a text editor, and largely defeated the purpose of moving to Ubuntu, but it nevertheless eased the transition.
As indicated, I do suggest Ubuntu, which I think is the best developed and most usable system, not to mention having the largest userbase and hence array of help and software.
You'll find it a bit off-putting for a minute, a number of aspects, particularly installing software, aren't exactly designed for ease of use, but push through. In a week or so you'll be comfortable enough to live with it, and in a month or two you'll be familiar enough to make a sound judgement between the two.
One note - one of the killers which kept me from using Linux for years was the lack of driver support. In particular I could never get my wireless card working, which rendered it a non-starter. This seems to have been cleared up as of ubuntu 9.10, but I'm finding some of the trouble over again with 10.04, the latest release. I don't know if it's hardware-specfic or just an issue with the operating system, since it's still in early days, but try 9.10 if 10.04 doesn't work.
Trying something new might be fun at first, but Linux can wear on you after a while. The inability to use your Windows programs, spending hours looking up small issues with the O.S. and other things get old.
After a while I decided that I could care less about using the Linux GUI and I really just wanted a console. This is served fine with virtualization.
My suggestion, install Virtualbox and run Linux as a VM and log into it with a console.
I suggest you to try the latest Linux Mint distribution, which is a Linux based on Ubuntu 10.4 and compatible with it. See: http://news.ycombinator.com/item?id=1375033
It's a bit more user-friendly that Ubuntu, which is also a good choice, and comes with Flash, mp3 support etc. out of the box.
If you are set to install Linux as your desktop, Ubuntu is as good a choice as any, if only because it is the most popular and thus probably has the largest support base. In reality, the primary difference between the various Linux distros comes down to where things go, how applications are installed/upgraded, default settings and the like, so your first choice shouldn't make much of a difference.