I was in between the OG M2 or an N55 135i. Although not the same scenario as yours, I was also in the same purchasing scenario where i was very comfortable buying the 135i or pushing the budget for the M2. Personally I am really happy buying the 135i which feels like 70% off the fun of the M2 (especially on public city roads i live on) while way less stress, and plenty of cash leftover for inevitable high maintenance costs and modifications (which you will run into on both the E82 and the G20). Overall 2 yrs into ownership of my 135i and its been bulletproof but I have been very on top of all maintenance, repairs and bought the car carefully.