I wouldn't space the cans out any further than a 6' x 6' grid. Dim them in a few zones. Get the regular incandescent/halogen cans for now, replace with LED lamps in a few years. Saying you need less LED fixtures is a myth. Look at the lumen output of both to make your decision- lumens are the measure of how much light the fixture produces. Even if the LEDs produce more light, you will still be limited by the light distribution of the cans. If you space them too far apart, you'll have bright spots directly below fixtures and dark spots between.
Look at the installation instructions on a Lutron Maestro dimmer for example. You have de-rate the number of watts the dimmer is good for when mounting multiple dimmers in a multi-gang box.