The aerodynamics argument makes sense but I don't think you'll notice a huge difference between a capable estate car and an SUV. SUVs are usually heavier which helps with towing. Having said that, the Mercedes-Benz E-Class All Terrain has a kerb weight of 2010kg - just as heavy as many SUVs. Generally, we advise that you tow no more than 85 per cent of the car's weight, so that'll leave you around 1700kg - enough for a small four-berth caravan. If that's enough, I think the E-Class All Terrain would be a superb choice - it's a really lovely car. The Q7 is very good but, surprisingly, not much heavier than the E-Class.