Hi Ann,

Aside from the engine/fuel decision, there's a vast difference between the Tiguan and the T-Cross. The former is much larger inside and out and it feels more substantial and more luxurious. It will also, assuming we're talking about the same model year, be more expensive. 

That aside, I'd be inclined to suggest that petrol power would be a better bet for you in the long run. It's likely to mean lower maintenance costs, even if the diesel car would be a little more economical on the longer journeys.