I'm considering both and I like the idea of extra seats and decided M2 was a bit steep for me. Besides the 240i has the B58 engine with a bit more torque and theres not much in it in a straight line between M2 and 240!.
I also like the Mk1 Nismo as Ive had the mark 2 before, fancy looking at the older nismo without the Recaros which were the main selling point in the mk2. After seeing R13ards one at Ace Cafe I thought maybe.
The MK1 will obviously drink more but will be rarer and the BMW I would get in Auto even though Im more of a manual driver. I did read some issues with infotainment system. But other than that pretty reliable. Not sure now lol. Both are around £20,000 to £25,000 roughly for 16/17 BMW and 14 plates Nismo respectively.
369 ft/lbs/335 HP BMW 240I - 4.5 secs Auto
270ft/lbs/344HP 370Z Nismo (Manual only) 5.2 secs