i always just presumed they were the same thing. maybe with seasonal they get more than one shipment of something, as opposed to a one shot
I think the difference is in the length of production time. Seasonal vernis colors are produced for a certain period, say, six months, and that's it. LE pieces have a limited order, so when that order has been produced (for example 1000 pieces), production stops. These are all hypotheticals, but it is easier to find a seasonal item than a LE item.