I run Ubuntu for three years now as primary OS at work, as this is the easiest for website development, with a local webserver running. This resembles the production server the most. Well I thought so...I don't dualboot or anything like that. I do use Virtualbox frequently to run XP. This works really fine for me.
On the other hand, I could have used Windows 7, with a local Linux VM as development server. I can't say that one option is better than the other, but that last one would have been closer to the server - no gui, exact version of linux, although it never will be identical. I've had my crashes with Ubuntu, different problems and issues. The guest OS has one big advantage: snapshots. I can use any software on my guest OS, and if I don't like it, I just restore an older snapshot.
So you have to make up your mind. Do you use many Windows specific tools? Ubuntu or Redhat just work differently than Windows, so that will take time. For me that was an extra reason, as I wasn't that familiar with Linux, this way I forced myself to get used to it.
I can't say that you should do this or that. Maybe if you were a colleague, working here, than it might be easier to use Linux, but even here colleagues just do what they want and some of them use Windows or a Mac.
And why only one partition? You can resize them if needed. Especially if you have a spare disk equal in size, you can make an image of the disk before you resize it, so you can go back if something happens while resizing.