The difference is that they play a different part. Usually the first violins play higher and have more melodies. The second violins play a bit lower and have a 'middle' part.

Is it better to be first violin or second violin?

The simplest answer is to say that usually the second violins play a supportive role harmonically and rhythmically to the first violins which often play the melody and the highest line of the string section. ... All first violinists appreciate the value and hard work of the second violins.

Is 1st violin harder than 2nd violin?

That said, the first violin part is often considered "harder" because typically it shifts to higher positions and can have more virtuosic stuff in there. ... Easy or hard, it is true that first violin parts tend to have the melody and spotlight much of the time, with the second violin in a more supportive role.