A Dell Venue 8 Pro with Windows 8.1 is about $150-$200 (and is a damned nice machine, surprisingly enough.) I'm having trouble seeing the use case(s) for a headless Intel PC.
The headless Intel PC has the benefit of being easier to conceal in the car. I could put this thing in a nice fan enclosure and put it under the passenger seat or equivalent out-of-sight place. Not to mention, the Intel headless PC looks smaller than that of any laptop out there. Each to his own though.
The Dell Venue 8 Pro sadly is $300 here in Australia. Obviously given the low Australian dollar, buying it overseas and shipping it will cost over $300 for me.x