You forgot Kreen, as well.
I personally think Askai is the best Jungo 5 star because his attack manipulation actually helps him to win. If he gets hit by SOA, he's still a solid 7/9 (with the bonus).
Meanwhile Adler, who does have higher power, does less damage compared to our samurai bunny when he is not hit by SOA and is predictable when setting him up to do so (he is pretty cool when you're up against a GHIEST or Roots clan, don't get me wrong!). Personally I think Adler is replaceable by Scotty.
Nahema hits hard and is a nice 8/8 but she is ability reliant, so SOA clans/ abilities wreck her and reducer her to 6/8. That's an acceptable power, but with a bonus that does not help you win, 6 power is kinda shaky.
Eduardo creates a lovely 10-12 life gap, but he has no support to win, meaning you have to overpill like made to get through.
Kreen, like Adler is best when hit by SOA, which could be difficult to pull off. Without SOA, she can create a 7-9 life gap, but with SOA she creates a beastly 12-16 life gap. However, her ability is ruined by DR (think of Arno, Yookie, Jeena). Basically Kreen is similar to all the other 5 stars (excluding Askai) who have no support and are forced to overpill to win.