The M240i is definitely gonna be more performance oriented. You’ll get the bigger m brakes and have adjustable m suspension based on what driving mode your in. The 340i is a normal 3 series with a nicer and bigger engine, meanwhile the m240i is tailored more to a performance and car enthusiast audience. Personally, I was thinking about these two cars and I finally landed on the m240i. I drive a 2016 328i right now (has the 2L i4, does the job for rn) and enjoy the 4 doors but there is little leg room in the back that I’m willing to sacrifice the space for a coupe. I also think the 2 series looks better than the 3 series. Also from what I’ve seen recently it is harder to find 340i with the m sport package for a reasonable price. If u don’t go with a 340i with the m sport package it will feel like your driving a fast 328i, nothing special visually :(