The Beretta is more accurate but Smith and Wesley is more powerful
There is no one best of anything, including various firearms. I would suggest that you make your choices among makers of better quality firearms. Typically that would include companies such as Beretta, Colt, Smith & Wesson, Walther, and the like.
Each performs as it was designed. "Better" is a subjective term for the most part.
beretta makes the m9.. you may be talking about the same thing.
Each performs as designed.
Beretta
Which Beretta are you talking about? If made to the same specifications, the only real difference would be cost.
both are good so it has to be shooters choice
No way to answer without more information. Both are fine weapons.
better to have a gunsmith assemble it so nothing is broke
Your question is impossible to answer without at least two types of firearms mentioned.
You stand a better chance of being killed by a doctor or drunk driver.
the fuel produces has higher ignition temperature and produces more heat