"what bullet weight and powder everyone likes? The why...."
Many like 180 grain bullets in the 40S&W.
I feel that the range is going to be short if used for anything other than paper and a little added velocity to expand is nice. So, I load 155 gr Hornady XTP JHPs. I've used Unique and Tightgroup but favor 231/HP38.
I also load 155 gr lead to the same/very close velocity using 231/HP38.
The whys are not as easy. The lead load to the same velocities as the jacketed is because I'm cheap and get a close recoil, bullet drop and follow up practice (I shoot double or triple tap). I run these in an XD SubCompact with 3 inch barrel, so greater velocities are not in the cards (yes, I can push them but not in my comfort zone). This nullifies my 'greater' velocity excuse over the 180 grain pills. So the why has to come down to, because I want to.
If the little thing wasn't so small and didn't feel/shoot so well... I like my 1911A1s... But....
Tribulations.