The SC-IV can sound great with a 10-12' separation, probably 8' would be minimum for the speaker's soundstage potential. But they should also have at least 3' to the sidewalls. And smoothest bass will be realized at least 3' out from the front wall (but not the same distance as from sidewalls). I talked with John Dunlavy a few times at shows and he always demoed his speakers with wide separation and good distances from adjacent walls.
The 3.6, being a dipole design, requires at least 5' distance from the front wall to achieve the recommended 10 mili-second delay between direct and reflected sound for optimum clarity. It may be possible to place them closer but either diffraction or absorption will be required behind them on the front wall to simulate that distance. Fortunately sidewall distance is not critical.
Otherwise, the SC-IV can sound spacious when set up correctly, but not like the Maggies. And while I've heard reasonable bass from the 3.6 it won't compare to the SC-IV.
Individual choice is always personal so I hope this all can help your decision.