As much as I despise Kamran Akmal the guy and hated his wicketkeeping, he has been instrumental in playing some of the best knocks for Pakistan in t20is. His peak was 2008-2010. A very short one but during that time, he was good enough to be one of the main guys for Pak's wt20 09 win. Kamran was probably the third most important guy in the team for that tournament after Afridi and Gul. He consistently provided fast starts in that tournament. In the semi final, he got Pak off to a flyer (relatively speaking considering the pitch) with his 23 of 12 on a pitch everyone else found it extremely hard to score. Afridi did exceptionally well to get a 50 but Pak wouldn't have been able to get to 140 odd if it weren't due to his cameo. In the final again, Shahzaib Hasan was struggling to put the bat on the ball and Kamran took away all the pressure off him but consistently taking on the bowlers scoring 37 or something and giving Pak a good enough start from Afridi to capitalize on and take the team home.
He was again very good in wt20 10 as well. Pak was something like 40/4 in 10 overs against SA before Kamran and Umar counterattacked and took Pak to around 140. In the semi final again, he played a great knock alongside Umar but Hussey played a mercurial knock to trump it.
He also played a little gem against Australia in Australia in 2010 scoring 60 something at a SR of around 200 chasing 120 something where no one else was able to score more than a SR of 100.
Kamran was an awful keeper and when he was hitting his peak in 2010 as a batter, the spot fixing saga and his 6 month long axing from the squad put a total end to his career. After that, he was simply a passenger. Kamran was only useful when he played as an opener in t20is. As a middle order batter or finisher, he was awful.
Kamran was never consistent and his numbers prove that but on his good days, he was probably our best opener in t20is and a wt20 victory is a feather on his cap.
Coming on to Rizwan, he isn't the most talented batter in Pak and has punched above his weight and is seemingly has just started to get better after a stellar year as an opener. Rizwan has some visible chunks in his armory but he has been gritty enough to somehow make up for them. On pure numbers, Rizwan is the best batter in the t20i team as of now, and him not being aggressive enough up front or taking a bit long to get going has some merit in it, but the thing is there isn't anyone better to do that job over and over again considering the joke of a middle order we have. Although Rizwan has played more t20is than Kamran, he still has more games left in his career and is a great opportunity for him to take Pakistan to a world title.
Based on who should get into the team depends on what the team lineup is. If you have a middle order of peak [Afridi, Malik, Razzaq, Umar Misbah, Hafeez, Younis(Misbah and Younis were very good in the early period of t20i format when it was still taking its shape)], you can take a punt on Kamran and hope for him having a good day to take us off to a flyer.
But when you have a middle order of Shan, Iftikhar, Khushdil and Asif, playing Kamran would be a suicide as he will fail on more occasions than not and Pak will bundle out for around 130 on most days.
Rizwan is crucial for the current team and Kamran was crucial for the 2008-10 team as the respective openers.
Regarding adaptability, Kamran never showed the adaptability when the middle order of the team got weaker from 2012-14, and we remained an ordinary t20i team during that time.
Rizwan has time up his sleeve to show versatility in his game and if he can help Pak win a title, he would be an undisputed pick in the team.
But honestly speaking, the middle order that we currently have is not going to win us any tournament.
