Confused now - so you needed a left-hand positive? That does make it harder to find. Otherwise, great deal on a yuasa battery, especially from a dealer. Around here, they tend to try and charge as close to msrp as possible.
Aside from only being available in a factory activated design, the 20H battery weighs 15.1lbs vs 13.9lbs on the regular 20. Other than that, both are specd at 18ah. so aside from a marginally shorter overall service life (as the battery's capacity and conductance decrease), there's not much difference in most applications.
Being dry-charged vs factory activated and sitting around for who knows how long could definitely be a plus