I'll give you my experience, but I'm no expert. We've had the United Airlines Miles Visa since 2004. It has an annual fee of $60, but the first few years DH's work reimbursed us for $50 of it. We try to put almost all of our expenses on the card - from gas and groceries to cable and cell bill to one time large purchases. We accrue a mile per dollar, and generally a domestic ticket costs 25,000 miles. There are special ways to accrue miles (like dining, or spending at certain retailers), but I don't pay too much attention to that. In the 7 years we've had the card we've flown 'free' to Maui, Ireland, Denver, Vancouver (3 tickets including DD), and I had one ticket to Orlando. Plus right now have enough for 3 domestic tickets still. I've never had a hard time using the miles, but I am a planner. For Maui and Ireland I booked those the earliest I could (like 11 months). Sometimes the flights aren't super desirable (for Vancouver we have to change planes in Denver) , but we still get there!
I've looked at the Disney card, and for us we feel the flights make more sense at least right now. With any rewards cards it makes the most sense to pick one and stick with it! Also, a lot of them have bonus miles for signing up. You can shop around for them. Depending on where you live you'd probably do best picking an airline that has a 'hub' near you (like if you're in Denver I'd choose UA).
We do live in a HCOL area, so our monthly expenses might be higher than most. Lately our bills have averaged $3K a month

, but we pay it off every month and have never paid finance charges
(save for the time I used the card just to get travellers checks for the miles which counted as a cash advance - lesson learned).
Good luck!