As a recap, a base 228i starts at $32,100 not counting a $925 destination charge. It includes 240 horsepower, 258 pound-feet of torque and, when optioned with the six-speed manual rather than the eight-speed automatic, a perfect 50/50 weight distribution (the 8AT balances at 50.3 in front and 49.7 in back). The M235i, meanwhile, starts at $43,100 (although you can't actually buy one for that, because the configurator forces you into a $1,450 Dakota leather interior). It offers up significantly more grunt, with 320 hp and 320 lb-ft from its 3.0-liter, turbocharged straight six.
Click over to the configurator and play around.