It depends on what you want to run, and how tech literate you are. If you have asked this question, i assume that this is your first time setting up an off road GPS.
I've had everything from a Laptop with Ozi on it, to HEMA navigator to the VMS gps products. They each have their own pro & cons. My advise would be to stay away from Ozi. It's popular due to that you can get "free" maps with your mates which is not really legal but it has the WORST user interface ever. You'll also spend hours been frustrated with it.
Recently, I bought the
VMS app for my iPad and a ram mount from GPSOZ. It's by far the easiest to use and impressive software i have used. The iPad is also unbeatable due to the size of the screen. I highly recommend exploring this option. The cool thing is that you can also use the iPad for email, internet and so many other things so it's well worth the investment.
Roger out.