Well you know how you have different Pokemon types right? fighting, fire, water, etc ...
Sekirei seem to be the same, some have control over the elements as others are more "fighting" type.
Also as Pokemon is about "catching then all" Sekirei plan was about winging Sekirei so the one with most Sekirei have better choices of winning.
The Pokemon is more of a joke about how Sekirei were Pokemon-like with their element attacks or pure fighting skill and how Minato had to "wing'then all".