Both are great vehicles. You'll have more room in the front/back seat of the Passat. And, believe it or not, more storage in the trunk/tailgate of the Passat. I've found that the Tiguan isn't useful for hauling things around, unless you fold down the rear seats, but I always had passengers with suitcases, golf clubs, etc. Very difficult.
If you don't care about fuel economy, the 3.6 is a great engine. Very fast. Probably too fast for a FWD car, if it's anything like the 3.6 in the previous Passat model, without the 4motion.
I would suggest the Passat, for the roominess, if for nothing else. Good luck!