My Pfaff 1471, 1473, and 1475 are"older" - but they are early computerized machines - and they use either plastic or metal. I can't tell any difference in performance.
I also use plastic or metal bobbins in my other machines. As long as the bobbin is the correct style/size - my machines are okay.
Some machines, though, may have definite preferences. Check the owner's manual.
But - the recommendation for your machine may be to use only plastic bobbins.