A Herringbone parlor is the most common choice when choosing a "smaller" parlor. In a herringbone parlor, the cows are facing away from the operator in an angled or "herringbone" position.
As important as your cows may be in the milking routine, so is the milker. Support arms help carry the weight of milk hoses and milking units so your milkers don't have to deal with the strain in their shoulders and lower back. This could potentially save you in time paid for labor because a sore milker will most likely move a lot slower.