It's difficult the measure one's best, but if we go only by games against our biggest rivals in England and Europe, Bernardo is more impactful than both Yaya and Silva.
CL quarters and semis: Bernardo 5 goals, Yaya 0 goals, David 0 at City (1 at Valencia).
Anfield and Old Trafford: Bernardo 5, Yaya 2, David Silva 3
So, against the very best teams and at the most difficult grounds Bernardo has outperformed both Yaya and David Silva: as many goals at Anfield and OT as Yaya and David combined, and 5 times more goals in CL quarters and semis than Yaya and David combined.
If one measures the best in performances against the best teams or at the most difficult grounds, Bernardo is better than them both. Add to that that Bernardo's work rate off the ball is superior to theirs.
Even if Bernardo isn't better at his very best than them (because football is more than goals and working off the ball), he's much closer to them than many realise.
For me, If Pep is offered one from Bernardo (or Gundo) and Yaya, he goes with Bernardo every day of the week.
Maybe a thread is needed: how good was prime Bernardo?