The rank you will be at retirement will always change. It
is true that men join the army for ranks, but most importantly, you
need to have the passion to get it through, and also 'a little bit'
of patriotism.
In term of money, of course Architect will have better prospect,
but commando is a very different vocation.
By the way, I know a Major who had a MBBS, but choose to serve
as a Commando, combat officer in the field. But when he was
'too old' for field deployment (about 40, by then, no much field
appointment too.), he left and practice medicine. BTW, that
man is a weirdo, rare and unique, truly passionate about soldier
life.
So, bottom line is, even if you want to be a commando officer,
do not forsake your study too, for one day, you cannot perform the
job anymore, you will have something to fall back to.
Cheers,
Old man.