Wrong , M-16 was selected some 30+ years ago than abt 15 years
ago, MAF selected the Steyr AUG to replace the M-16A1 in the
regular army and the old M-16A1 is relegated to part timer
TA.
So Steyr AUG design must be better than the M-16A1 since it was
selected to replace M-16A1, at least logically, but for the case of
MY , you will never know!!! 
So is it logical in the first place for MAF to dump the old design
M-16 and then later go back to it again?
Anyway, your stated that becos MAF has used the M-16A1
before and due to logistically reason, therefore it is rational to
continue to use old design but upgraded M4!!!
That statement will be logical if they progress from M-16A1 to
M-16A2 but they did not, and 2ndly that is only evolutionary , not
revolutionary.
Therefore, to be revolutionary, you can't continue to use an old
design as newer AR come online, one must evaluate all that are
available to make the most cost-effective and rational decision,
that process could take years, just look at the US for the M-16
replacement (and yes US is also looking to replace their M-16 too)
and SAF becos you are talking abt re-equiping the entire armed
forces for at least 2 decades.
Therefore, one cannot be just select the old design just becos of
logistical reason, if there are better design AR is available and
within budget, then that will be the rational choice.