Neither....
Has almost virtually nothing to do with more sets less sets
Has everything to do with mechanical positions, tweaked exercises so you make them productive, and "getting weird with it"
If you have been training 8 years and your biceps still suck......lets be honest....you have done thousands of sets of barbell curls, dumbell curls, standing seated and the "basic curl movement".......obviously that "basic curl movement" isnt doing the trick is it...and doing more sets or less sets isnt going to do jack crap. <-----and this is where people get lost in the volume less volume tornado.
You need to think outside the box and get away from "what isnt working exercise wise" and tweak things and change things to find things that work exercise wise and then get very strong on them over time.
You could spend all day doing set after set of pulley pushdowns, one arm dumbell extensions overhead, kickbacks, and extension machine for triceps for 22 sets yet find out that Dips make your triceps grow like crazy and (in that sense again it is the exercise and not 22 sets of useless exercises that made your triceps grow)
For people who have chests that are stuck growing i usually start out with four things and go from there.
1) Set them up on exercises with their sternum raised high and shoulders back and make them press the bar lower than they are used to....like on an incline smith press....sternum high, shoulders back...and you have to bring the bar to the nipple line or a little higher which forces your elbows to travel downward.....and it will be awkward at first but youll get your self set up right....(if something just doesnt feel right safety wise you always scrap that nonetheless)...sternum high, elbows travel downward
2) get them on machines they arent used to or tweak them, grip width, seat higher, take them out of their comfort zone....always with sternum high and shoulders back
3) find a power groove exercise and bomb it. What i mean by that is i.e. like the leg press where you can use heavy weights and high reps and it can put you into a power groove where you can just grind it out.....id find an exercise like that for a weak bodypart and i would grind it out every single time chest is done for 20 reps.....
4) any exercise you can safely pause in the stretch position for 1-2 seconds is very beneficial (emphasis on safely).......sometimes i have guys use flat dumbell presses for the powergroove exercise in #3......I make them get up on their toes so they can arch their back and force their sternum high with ass on bench and shoulders pinned down and back.......i wrap their elbows on work sets with their knee wraps (not tight just enough) so their triceps dont bomb out before pecs...and i make them do 15-20 reps with a 1-2 second pause in the bottom position (chest high sternum high) and then press
its all about "getting weird with it" if you have been lifting for a number of years and the bread and butter exercises you and everyone have been doing arent doing the trick.....you have to change to something outside the norm mechanical position wise....and it has very little to do with "am i doing enough sets?"
If seated pulley rows made someones back respond and it was a productive exercise for them ....the best thing they could do is take that 150 x 12 pulley row and take it all the way up to 350 x 15 over time.
Same thing here.....get outside your comfort zone and tweak exercises, make new ones up, position yourself differently....get your form down right and then get very strong at them over time.