Here is what I have been doing with my Astro all week.
Really an Astro isn't really a minivan it is kind of in the middle of a full size van and a minivan and doesn't really fit well into either category. So a real FWD minivan will potentially get better mileage by a little bit and be smaller and easier to drive in a city. But if you ever wanted to do something heavy minivans won't be up to the task. I hauled that tractor 75 miles to the dealer to get the fuel gauge changed under warranty and the Astro had no trouble with it. For typical weight I am dealing with I would have been better off with a large truck but vans are much cooler than a truck so I make do with my little Astro. I reset my ignition timing back to the proper setting and with my radiator fan removed I am at 24mpg right now.
I would say you really just have to think about what you want out of your car and what you are willing to live with. If you actually sit down and add up the numbers from the mileage and estimated expenses you should get a pretty good idea of what will work for you. It pretty much comes down to total cost of ownership, purchase price, repairs, fuel, and maintenance all add up. So think of all the things you want to do with a car and figure out what it costs for each vehicle you look at. Sometimes the best mileage is not always the best choice. And sometimes you spend a bit more overall on a car because that is what you really wanted even though it wasn't financially the cheapest choice. Me personally I think my Astro is great for what I use it for. But I have my Metro to drive around in when I don't have 5 people going with me or hauling something heavy so that makes things different for me than it will for you.