in theory anyway, the reason moro krises is bigger than their indonesian and malaysian counterparts was because of the necessity in order to match the toledo blades of the spaniards. it has then been postulated that it was during around the era of Sultan Kudarat (reigned from 1619 to 1671) when the transition happened. the Moros had minor skirmishes with the spaniards prior to this era, but it was during Kudarat's when the three major tribes allied themselves for the first time against a common enemy.
the form of kris above (deep, pronounced and much narrower blades than their later counterparts) is regarded as the oldest type (referred to as "archaic"). i have a particular kris (http://www.vikingsword.com/vb/showt...ed=1#post143776
) that has a rounded tang, as oppose to the flat ones common to the later models. IMHO, this was a carry-over from when it was shorter and most likely similar to their indonesian counterparts. now the transition from the "archaic" style to the more common type is up for debate. now again, IMHO the reason for the transition to the more recent style would've been due to the widening and lengthening of moro kris.