Well, there's almost no technical pluses as except for not having save your print jobs to disk, or disconnecting and reconnecting your printer if you have the desktop and the laptop + docking station. It really depends on what you're going to be doing with it. I have a Dell Inspiron 8500 and it can play all of today's current games, but it can't play them as well as my gaming rig. The only Dell notebook that could truly even compare with a well equipped desktop is a maxxed out Inspiron 9100 (that's what they're calling the XPS isn't it), and even then, you can't overclock, install as much new hardware, and all that other fun stuff. If you're not going to be doing much gaming or graphics intensive apps, I'd say that a laptop plus docking station should do just fine. After all, I went for months with mine before building my gaming rig, and only then because it was in the shop! 
Jim
Jim