I would be happy with either player. Obviously the tragic loss of Jota means we need a striker. Either Ekitike or Isak would greatly improve on Nunez.
Be interesting to see how this little tug of war with Newcastle develops.
I will pick the proven Isak over Ekitike at least because has already adapted to the league, and he was great with Real Sociedad and his game didn't drop at Newcastle where the pressure was higher, Liverpool is different and the expectation would much higher, that's why I'm afraid Isak would be the better option, my only concern would be the lingering groin injury he battled with a lot last season.