Should I spend 10k more to get an Audi A3 rather than a Ford Fusion?

Both new, the audi A3 would cost me 11k more, and would have leather seats rather than cloth

I wouldn't. Not for the A3. Truly we can't tell you what to do with your money though, or which car fits your needs better. I've owned an Audi S4 which was a lovely car and I've driven a few Ford Fusions. Is the A3 $11,000 better than a Fusion? No, not in my opinion. But again, this your money.

Do some research on www.edmunds.com on the 5 year calculator and see what each car will cost you in the long term. Make sure you get insurance quotes on both cars BEFORE you buy anything.

Audis are unreliable pieces of garbage, though the Fusion doesn't have a good reliability track record either. I'm pretty sure you can option up just about any mid sized economy car with leather seats these days. A Mazda 6 or Hyundai Sonata are much better choices

Research what you want in your car.
How much will the insurance cost?
What is the resale value of the car?
What type of gas does it use? (regular or premium?)
How much is the service going to cost?
There are lots of questions when deciding, also you should test drive both cars to see what you like. It is not worth 11k to get leather btw. Just do your research and think logically.