OK, I'll bite.  I have over-thought this so it I'm probably wrong but it takes the same amount of line pressure to actuate your brakes regardless of line size.  You don't have much volume to fill in properly positioned pistons/pads, so you won't gain a thing with a bigger line.  Or, you have the same PSI and with 1/4 tubing you have more SI so you will probably get a very small increased tube expansion with the larger diameter line that could result in a slight spongy feel in your brakes.  The fluid is incompressible but the steel brake line is expandable.  3/16" lines are easier to bend, harder to kink, and probably cost less.   See, I thought about this too much.