Junemar is 31 years old as of this moment so provably he will be out of his prime when he face Kai in PBA once he choose to join in PBA but for sure there's a big difference between them since in experience for sure KAI will skills will prevail since he have lot of experience overseas with strong opponents compare to Fajardo. Even if Fajardo will be on his prime for sure he will shake his head once he face a young and skilled Kai in the court.
If ever that KAI choose to play locally match up between him and JMF is no longer that exciting, as mentioned JMF is no longer on its prime plus those injuries that he already have while KAI attends special practices and more advanced trainings abroad. Though the chance still slim since KAI really aiming to play to NBA and be the first pure blood pinoy to represent our country.
It's a big achievement for our fellow kabayan, he had the height and the skills all he needs for now is more exposures so media will hype his way to the NBA.
For the injury got by Junemar recently for sure there are changes for his game and provably he will not the same as before when he performs well compare to the past years but we cannot really compare since Kai and Junemar have different generation so for sure, there will be no competition among them. If we talk about skills for sure Kai is more advance since as you said he is advance since he plays and trained well in the US.