Yes, mine was the 35i with DCT. For me, the M135i is just so much easier to drive fast. It doesn't sound as good but the power delivery and handling is much better IMO.
Have you driven the M135 much?
Done a few hundred miles in a friends M135i when we went cycling. I didn't get much of a chance to try out the handling as we were fully loaded with kit. The N54 is quite spikey in comparison, but it was barely noticable for me. You definitely have more sense of occasion driving the Z.