Two team have quite big differences and we will never be able to equalize them, moreover Al-Qadsiah development will really be tested in the SPL competition next season, they will be under series of pressures against strong SPL team who always dominate.
Maybe Al-Qadsiah also has lot of money with the ease of bringing in some great European players, but that won't guarantee they can survive the really tight SPL competition, maybe they could also be relegated again.
We see how they prepare the team and start the season by entering the most important League in Saudi football, there are doubts for me about Al-Qadsiah being able to stay here for long.
Regarding Nacho, it is clear that money is his main goal, it is impossible for him to play with Saudi team just for low salary, but this is Saudi football which can always bring in lots of European players.
I do not think that they would be "tested" all that much, as long as they stay in the league then it is an achievement. I don't know if its different in the Saudi league or not, but in most leagues at Europe if a team comes from second division to top division, staying there for a few years is an achievement, nobody expects anything else.
Maybe afterwards they may start to ask for more, but even then sometimes they just want to stay. Look at Leeds, they have gone up finally but then went back down, or Watford, goes up and down all the time. So if its different in Saudi league then I don't know, but if it is similar to Europe then I can say that all they have to do is stay in the league and do not drop one level below for now.