I always suggest getting more truck than you need. Mostly for safety and reliability. If your truck is pulling a trailer that is at or near it's maximum capacity your on the edge of safety and the strain will cause premature or unusual failures in the engine and drivetrain.
My biggest concern is being able to stop safely in a panic situation and to be able to go down long steep grades without losing the brakes.
An f250 will probably get the same gas mileage around town empty and about the same when towing. The ride will be a little rougher but you can soften the ride by lowering the tire pressure when empty to acceptable levels shown on the tire manufacturers website.
The advantage of the F250 will be when towing...less sway, better control it will have bigger brakes for stopping and long downhills. The drivetrain components are designed for heavier loads so it should last longer.
And you'll be ready for a bigger trailer when the time comes.
