I ran OZi Explorer on a laptop and used a Garmin GPS via USB for signal - worked great and was the best setup I had in terms of mapping as like others have said Rooftops maps are so detailed, plus many local maps can be loaded plus all of the HEMA collection. Ozi is complex to use well but there are resources and courses out there to help. I believe most serious comp trucks run Ozi (and some even run a marine grade Garmin GPS as well).
In the absence of finding a suitable semi permament mount in my 100 series for the laptop, I retired it and use HEMA on my iPad with a RAM mount on the windscreen. RAM mount is brilliant and even though my iPad is the first GPS model it still runs HEMA maps well. I used HEMA Explorer and will be keen to check out v3.0 as they now have more scale available (currently overseas). I toyed with mounting my wife's iPad mini behind the drivers sun visor so it could be tucked out of sight when parked but hers was not a retina display and the text was a bit fuzzy on all apps...plus the bigger screen gives you a wider view of the map. The new iPad Pro is a monster but would be unreal if you could find a suitable and safe mounting position.
The best thing for me about HEMA (or any good iOS app) is that I can also use it on my phone on my KTM when trail riding. That means I have all of my mapping data (waypoints most important if I am out bush) in the cloud no matter what what adventure I am on. I have also retired my Garmin handheld due to the fact I always carry my phone and with the right app it does even more than the Garmin ever could. Hope this helps.