Flip a coin, spin a chocolate wheel, throw a dart....whatever the answer you'll be happy anyway the first time it's -5c outside and 20c inside! For me, I've installed diesel in our last 3 vans (plus another 3 in parents and in laws and a friends van) after weighing up our needs, for me it was: where I wanted it installed to retain useable space (not limited by regulations), keeping my gas exclusively for hot water and fridge (beer and wine) and I usually have a jerrycan of diesel in the ute. But they are my reasons and each to their own. Enjoy the warmth next winter!