I'm not even sure it even comes down to price. Whilst on paper, they offer obviously comparative points, they are two entirely different animals. The 370Z, is a two seater, track-honed sports car. The 135i, on the flipside, is a four seater, daily driver type car that happens to have a bootfull of go. The fact they offer similar performance times with respect to 0-100's and 1/4 miles is where the similarities end.
I know that if I were in the market for a two seat sports car, I probably wouldn't even consider the 135i. It's not a "sports car" as such - evidenced by the lack of LSD, the 2+2 seating layout, the "soft" suspension and RFT's. The article states Nissan were aiming at the Cayman and I think the BMW equivalent is really the Z4. You simply don't buy a four seater when you're after a "fits like a glove" two seat sports car.
I was cruising along the river the other day at like 45km/h, my mate commented on how quiet, comfortable and smooth the car was. It would seem from the article that the 370Z can't actually do this - evidenced by the reported drone and tyre roar. Of course, this argument is nullified at the track where the 370Z achieves better grip and cornering abilities.
Fact of the matter remains, Nissan have certainly improved upon the 350Z in many regards and have made a cut price track weapon and should be commended. On the BMW side of the fence, which is where I obviously currently sit also, I have a car which i can load 3 mates into (which I did as recently as two days ago) and enjoy a cruise in comfort, luxury and refinement, then drop them off, take it to the track and pass respectible times in, but not chart topping - all for a $72K buy in. The 370Z can only do one of those things, regardless of what price point it enters in at.
Proud new owner of a X1 23d in Jet Black