Every club in the Saudi League has strengthened their teams in such a way that it is difficult to distinguish between the big teams and the smaller teams. Ronaldo and Nasser play for the club and some other star players have joined the Al Nasser club so we consider this club as a strong club but outside of that there are clubs like Al Hilal and Etihad who have been performing very well. No match for Al Nasser is easy, every match requires a lot of hard work and proper planning to win. One season Al Nasser is the champion, another season Al Ittihad is the champion and another season Al Hilal is the champion, so there is still competition in this league and that is definitely a good thing.
It's easy, in order to know which are the big teams and which are the smaller teams depend on how much money they have, if they have a lot money, they're big teams and they able to sign European players. There's a competition in this league, but a competition among B class teams. 
If there's an A class team joined the league, they can easily win the league.
However, finances do not necessarily make them have the title of a big team, because some teams that have very good finances do not necessarily compete at the top. So this is something we have to explore further to say which are the big teams and which are the ordinary teams.
Likewise, teams with finances that are considered ordinary can sometimes also compete at the top, even though some of them also have problems with consistency. The Saudi Pro League has a rich team and that has been confirmed by their movements in the transfer market for example.