Can someone help me figure out the difference between some of the engine options for the 2017 Transit passenger wagon? I know very little about cars or engines, so I have no idea what I should be looking for. One van I'm considering has the upgraded 3.5L GTDI V6 and the other has the standard 3.7L TIVCT V6. It is a low roof, regular wheelbase and we won't be towing things, so we don't need a ton of extra power. Thanks so much!