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.
Beretta
Each performs as designed.
Which Beretta are you talking about? If made to the same specifications, the only real difference would be cost.
No way to answer without more information. Both are fine weapons.
better to have a gunsmith assemble it so nothing is broke
both are good so it has to be shooters choice
Your question is impossible to answer without at least two types of firearms mentioned.
the fuel produces has higher ignition temperature and produces more heat
Both are fine weapons. Best is to subjective a term to use when comparing them.