I can get the M8 secondhand for around £85, and the M9 for around £110. The M9 seemed like a no-brainer considering the price similarity, but the more I read about the two, the more I think the decision is not as clear cut. Here are the main differences as I see them: M8 Battery life: two days between charges with light usage; sips juice when in standby Camera: not great in general, but low-light performance not bad Performance: fairly snappy with Sense Android version: Marshmallow M9 Battery life: Pretty much dead by the end of the day, problems with battery drain under standby. According to user reports, this isn't fixed with Android Nougat. Camera: Better than the M8 in some circumstances, but worse low-light performance. Front camera not bad; uses same "Ultrapixel" architecture as M8 main camera. Performance: Higher-end processor, should be quicker. Overheating issues. Android version: Nougat Which would you go for? I'm actually leaning towards the M8 a little, but the M9 is newer and has a more recent OS without resorting to custom ROMs.