I have both! A e92 m3 and 335i jb3 both 6mt
Love the power and of 335i, I upgraded the steering wheel to the m3 version, as well as the weighted m, shifter. The 335i is great as a daily driver. Because the torque comes on very early, every bit of road is usable to enjoy so you don't need long stretches of asphalt to "feel the power"
The m3? Sounds amazing, looks good ( if lowered, still way to high) m button is fun. A completely different drive. High rev engine, power comes on late, but still usable. Needs a track or twistys to really show its worth. And lastly the "M" has pedigree if you care what people think ( which I don't) but I do like that it has some "history" to it.
With all that said, I might still sell my 335i for a 2nd m3 e93!, the convertible version of the m3 allows you to really hear the sound of the v8, which is addictive. But so is the low end torque or the 335i. You really can't go wrong with any of them!!
so much to say, but so few will listen