This changes periodically, but for today, here is what I would do.

My PowerHA selection process would be:
* 7.1.3 SP06 if I needed to deploy quickly, because I have build docs for that.
* 7.1.4 doesn’t exist, but if it came out before deployment, I would consider it. Whichever was a newer release, latest 7.1.3 SP, or latest 7.1.4 SP.
* 7.2.0 SP03 if they wanted longer support, but had time for me to work up the new procedures during the install.
* 7.2.1 SP01 if SP01 came out before I deployed, and had chosen 7.2.0 prior. 7.2.1.0 base is available, but that’s from Dec 2016, and 7.2.0.3 is from May 2017. Newer by date is better.

My AIX selection process would be:
* Any NIM server would be AIX 7.2, latest TLSP.
* Any application support limits would win down to AIX 6.1, plus latest TLSP.
* For POWER9, I would push 7.2, latest TLSP.
* For POWER8, I would push 7.1 or later. — latest TLSP
* For POWER7, I would push 6.1 or later. — latest TLSP
* For POWER6 or older, or AIX 5.3 or older, I would push strongly against due to support and parts limitations.

Code sources:
* I would make sure to install yum from ezinstall, and deploy GNU tar and rsync:
http://public.dhe.ibm.com/aix/freeSoftware/aixtoolbox/ezinstall/ppc/
* I would update openssh from the IBM Web Download expansion:
https://www-01.ibm.com/marketing/iwm/iwm/web/reg/pick.do?source=aixbp&lang=en_US
* If any exposure to the public net, or a high-sensitivity system, I would check AIX security patches also.
http://public.dhe.ibm.com/aix/efixes/security/?C=M;O=D
ftp://ftp.software.ibm.com/aix/efixes/security/
* I would get the latest service pack for both AIX and PowerHA from Fix Central:
https://www-945.ibm.com/support/fixcentral/
* Base media, if I were certain the customer was entitled, but didn’t want to wait for them to provide media, Partnerworld SWAC:
https://www-304.ibm.com/partnerworld/partnertools/eorderweb/ordersw.do

Reference: PowerHA to AIX Support Matrix:
http://www-03.ibm.com/support/techdocs/atsmastr.nsf/WebIndex/TD101347