I've got an '09 Fit. Sold our '01 civic to buy it. Both were 5 speed manuals. The fit gets a little better mileage, but not much, and the ride is worse. We drove my BIL's '13 Fit over the weekend, which I thought had a much better ride, and maybe a little less road noise. I'm sure some of that is the tires. Both are Sport models. On our last road trip, the Fit got 38 average with the AC on and driving about 75 MPH most of the time.
Honestly, I'd never drive a VW. I've got lots of friends who fell over themselves to buy them because of the fuel economy, and the darned things are in the shop way more than they should be. Also, they suffer from a tendency to have little stupid things go wrong that don't really warrant repair in many cases, but add up to a quirky car. Also, these cars are pretty expensive compared to the Hondas and Toyotas.
Yeah, the diesels will get a little better mileage, but I think it's silly to look at that solely. Diesel has cost more over the last 5 years. Between my last three cars, I've put about 160,000 miles on Hondas with hardly a trip to the shop. I did the timing belt/water pump on our civic at 100k, and did the front wheel bearings. I had the rotors turned on the car before that, a '93 accord that my dad now drives. That's it. By the way, that accord has 285,000 miles on it. The clutch is original. His previous accord, a '92 had 275,000 on the original clutch when he parked it due to rust issues. All of these vehicles have been dead reliable. I'd happily trade a few mpgs for the reliability of a Honda versus a VW.
Going from a CRX to any of these cars will be an incredible upgrade, but I'd still say to try several to find one that rides the best. My preference would be for the simplest car, I.e. a basic gas manual hatchback. They however will ride worse than a Prius or diesel VW, because they are lighter cars with smaller tires. I'd be looking pretty hard at corollas, yaris, fit, and civic.