agreeing with the above, i've kept both a lei and a jar at different times
apart from physical differences - leis are slimmer, more silver and have spots on each scale, jars are thicker, darker and have a more of a 'spoonhead', there's also a differences in temperament.
it could just be the fish's personalities, but my lei was more placid, calmer, even ate from my hand, while the jar is a MEAN sob, constantly attacking me through the glass..
pricewise, in melbourne leis and jars were selling at about $100AUD for a 4 incher, but i havent seen leis for sale in YEARS
unfortunately my lei jumped out of the tank while i was moving house, he was 20" at the time.