I was faced with the same choice when I bought my SM. At the time, IM and SM were both available. BDK as well.
I went with SM. My first and only NIB purchase. Haven't regretted that decision. SM has good depth with different opportunities/strategies to max points. It's fully featured and build quality is solid.
IM is a rush and you really cann't go wrong with either. I went with SM and still happy with that many years later.