Breeding het pied x het pied will statistically yield a ratio of:
1 piebald
1 normal
2 het pied

More plainly, you have a 25% chance of producing a pied when breeding two hets together. There is a 66% chance that the normal appearing offspring are het for pied. While het piebald snakes often have a visual marker it is not a 100% guarantee of genetics.

The amount of white in the parents has no effect on the amount of white in the offspring. Low white parents can produce high white offspring (and vice-versa). You will also have a wide amount of variation in the same clutch.

High white pieds carry a higher price tag (for obvious reasons). Low white pied are often more competitively priced. If you want pied purely for breeding you can save yourself some money by buying a low-white pied. If you want an exceptionally beautiful animal, go high white.

Cheers,