It seems that every forums on the planet are comparing aki sora with kiss x sis. Then, I shall give my comment here.

Story/plot organization: Aki Sora is better than Kiss X Sis because Kiss X Sis story is not that strong but rather more focus on cockteasing the reader/viewer with loads of fanservice scene. The only plot that Kiss X Sis has is the sisters trying to win their brother's affection, rivals each other while keeping their other rivals at bay. Aki Sora on the other hand shows the interaction between Sora and other females who each have their own issue to deal with but somehow they are all attracted to Sora. And so in terms of plot and story, Aki Sora wins.

Drawings/Art: It depends on which you're familiar with but for me I like the females artwork for Aki Sora and also like Kiss X Sis's males art work. So in terms of artwork, it is a tie.

Protagonist [main hero]: I am torn in this one because both are unique but also shares the same traits, indecisiveness but in terms of indecisiveness itself; Kouta is more indecisive than Sora. Why? Because Sora focuses/likes Aki while other girls drag him around while Kouta; we do not know who he likes in his harem and also being drag around by his sisters. Balls? both have balls but can't fight or express their opinion on their harem but Sora loses in this point becase he is somewhat girly and do house chores while Kouta is an athlete. Again, it is a tie.

For me, Aki Sora is the winner.