Important point to consider is that you won't get the 'proper' SMG, as
is found in the M3/5.
What you get with the vanilla Zs, 3s and 5s is a cut-price version of
SMG, that has received a severe slating from many reviewers.
I personally prefer Steptronic, and would never consider the cheapo-SMG
offered as a marketing gimmick in the non-M cars. On the Ms though, I'd
take the (proper) SMG over the manual any day.