Even though both of them don't look very good at the moment, Barcelona's performance in the Champions League cannot be underestimated, while Napoli experienced a much worse decline compared to Barcelona, but at least both teams still have a chance to qualify for the next round. If both of them are able to perform the best and surprising I myself really support Barcelona because in terms of squad and experience, Barcelona is further ahead of Napoli, so I might favor Barcelona more, but that doesn't mean I underestimate Napoli, it's just that this match is a little difficult for of us to predict.
Barcelona and Napoli now have their own problems. For the decline I see Napoli as having the worse decline, we can see that in Serie A. To be honest, I always use the domestic league as a measure, even though it's a different competition, but in the domestic league they have a schedule every week, so we can look at them and judge every week, whether they have decreased or improved.
I agree with you that it won't be easy to predict this match, and it's possible for them to beat each other and it will be their goal productivity that decides it. Both Napoli and Barcelona will have to watch out for each other.