Paper towel will break up if you have to scrub and i dont like the windex cause its a chemical, Im a worry wart and worry about it getting in the tank. The vinegar wont hurt anything. Not sure windex would hurt anything either but never chanced it.
I use windex on occasion- but I make sure its the last thing I do on the tank fro the day, and dont spray it anywhere near the tank. I spray it on the paper towel, far away. Then go clean the outside of the tank.