We need to look at the bigger picture.
Wilson got an extra two goals today, but both were pens, and they were both technically won by Isak. Isak is providing so much more value than Wilson right now despite not being in his preferred position. Definitely a better all round player.
Created Wilsons first goal vs Southampton, won a penalty today, came closer than Wilson to scoring vs Arsenal.
Wilson is a good goalscorer, but he's limited in terms of his all round ability.
If we're going to drop Wilson or Isak, it has to be Wilson. He has more goals overall but has played more games, and his tally involves more pens, and his all round play is not as good as Isaks.
You don't pick a player for our upcoming games because of what they've done in the past specifically, you pick them because of how effective they are likely to be going forward.
If I had to choose to start Wilson or Isak, it would be Isak