In continental competitions, there can be some indicators of relative strength. For instance, the top Spanish teams have dominated European Champions League so they are regarded as the strongest. However, how does the 3rd and 4th place Spanish League teams compare to the top 4 in other leagues? Head-to-head competition gives clues but it is hard to be sure. Anyway, it is this concept that drives the "UEFA club coefficients" which is the soccer analog to NCAA basketball's RPI. From those stats, one can see that the 3rd and 4th place Spanish league teams compare very favorably to the rest of Europe.
But when you get beyond the handful of top teams in the top leagues, it gets harder to compare. And it is even tougher to compare MLS in the USA relative to what is happening in Europe.
One attempt to rate strength is "market value" of players and clubs. Using the wisdom of the crowd the German web page TransferMarkt.com rates teams and players.
What I've done is do screen captures of the top 11 players of an assortment of clubs. Note the "market value" of the players listed are in Euros and they do not correspond to their actual salaries. Rather it is a rating of how much the player might gain in an open market sale of his services.
Here are the numbers for Brentford FC, a mid-table club in the English Championship (2nd tier).
Here are the numbers for Elfsborg IF, a mid-table and sometime competitor for the top part of the top league in Sweden (Allsvenskan).
Here are the numbers for LAFC, a new club in MLS in the USA.
Here are the numbers for LA Galaxy, the established MLS club in Los Angeles.
Finally, here are the numbers for Rosenborg BK, the top club in the Norwegian league (Eliteserien).
A few observations about the numbers from these 5 clubs:
LAFC and LA Galaxy have some very high market value players.
Once you get past the highest market value players (the top 2 or 3) in the two MLS clubs, the market value of the players are somewhere between Rosenborg and Elfsborg.
In fact, the 11th ranked player on Rosenborg's roster has a market value that would be 4th highest on LAFC and 6th highest at LA Galaxy.
The highest market value player at Elfsborg would be 3rd highest at LAFC and 6th highest at LA Galaxy.
Rosenborg has consistently higher market values across its top 11 compared to Elfsborg.
Brentford has very consistently high market values across all 11 players compared to the other four clubs in this discussion.
Based on market value, who would win on the field?
Brentford across its top 11 has higher market value players. However, LA Galaxy and LAFC have one or two specific players that have higher market value than any Brentford player. Since soccer is a team sport you would think Brentford would win.
Based on market value, you would think Rosenborg would beat Elfsborg.
The comparison is most difficult in regards to how LA Galaxy and LAFC would compare to the other three. LA Galaxy and LAFC have one or two players that are stronger than any of the players at the other three clubs. But players 2-11 or 4-11are somewhere between Rosenborg and Elfsborg.
In a group stage of LAFC, LA Galaxy, Rosenborg and Elfsborg, who would win?
And in a best of five match up against Brentford, how would LAFC and LA Galaxy do?