[Bc2005]

Current BMW 430i ( 4 cylinder) or M440i (6 cylinder) are 4 series, gasoline engine vehicles and they are all 2 door coupes or convertibles.
The 3 series 330i and M340i are the same size, but are sedans.

The M340i is one of the BMW “M performance” vehicles, which means higher performance, but not a full M vehicle.

The i4 is a 4 door all electric vehicle that is nearly the same size as the gasoline 4 series. There are both single motor (2WD) and dual motor (AWD) versions.

M4 ( M and a single digit) is the high performance 4 series vehicle and it has a completely unique engine tuning, etc. it is also much higher priced.