Laptop or desktop

I have just downloaded Sketchup 2016. I have only been using Sketchup for a little over a year. I am a landscape designer, where we specialize in hardscape projects, so I have found Sketchup to be a very valuable
with our presentations to our clients. My company is thinking of purchasing a new computer for my needs. I currently am using my own laptop, a Dell XPS 17 2ND generation . I know the graphic card is not ideal, being a NVIDIA GeForce GT 555M 3GB with optimus. I also know I cannot upgrade a graphics card in my laptop. Any information if I would be better off getting a laptop, or, perhaps a desktop, so if I need to upgrade anything in the future, as Sketchup changes each year. I rarely have used my laptop for presentations at the clients office or home. Also, any recommendations on a graphics card would be appreciated. Thank you so much. Happy Turkey Day to all!

for the budget, desktop is always best bang for the buck.
graphics card, just some GTX lines from NVIDIA will do. SketchUp doesn’t really support ATI cards well.

I currently own XPS 8800 which i bought 3 years ago, still runs well with some upgrades that I have done.