If you put it on the negative side the ground of the chip will be one diode drop above the true ground (relative to any part of the circuit outside of the diode)
If you put it on the positive side, the +VCC line will be one diode drop lower than the actual VCC (affecting all I/O pins in both cases)
I'd lean towards the + side to avoid the biased ground myself, for the sake of interfacing with the rest of the world at least. An extra diode drop to the VL of the logic might be high enough for some external components not to read as low, and will produce a small additional bias current.