Best speed/power: daisy chain
There will be no brightness difference if you daisy-chain all of your LED drivers.

There might be a speed difference, depending on how you're driving the serial interfaces.  


Multiple parallel devices, read or written in parallel, is potentially faster than a long daisy-chain.
Multiple parallel devices, read or written sequentially, will be roughly the same speed as a long daisy-chain.


For example, to write to the LED drivers in parallel:


Connect all of their clock pins together, to a single pin on your MCU, e.g. RB7.
Connect all of their LE/#OE pins together, to a single pin on your MCU, e.g. RB6.
Connect each of their DI pins to a seperate pin on your MCU, preferably contiguous port pins, e.g. RB5..0


To write, bit-bang as you would normally, but set all 6 DI pins before toggling the clock.

Reading is much the same, but reading from DO pins instead of writing to DI pins.

There is no guarantee that this will actually be faster than your original approach; any gains would mostly depend on how good you are at coding the bit-banging.  However, if your MCU has a parallel port that can be driven by DMA (like some of the higher-end PIC24's, for example), you can use that combination to read/write at speed, at least one and possibly two orders of magnitude faster than bit-banging.