Your answer is here.....
Bsc Physics is core discipline and you will understand all aspects of physics while Bsc PCM includes all three subjects in constant proportion and you will have a taste of Physics, Chemistry and Mathematics.
When you enroll in Physics for your graduation,you will get your degree as Bsc (Hons)

When you opt for PCM combination,you will get degree of Bsc.

There isnt any major difference between them as Honor's students also study some basics and major parts of main & subsidiary subjects.

Universities have different criteria for this, as in Banaras Hindu University,you have to choose the combination of three subjects whereas for Delhi University,you have to choose only one single subject for graduation.

As both are graduation degrees,both are equal and there isnt any advantage for a particular one.