Football is a contact sport or it's not a contact sport. It's obvious La Liga plays and officiates in a way that discourages body-on-body contact like in England, Scotland, or Germany. There's no debate on this issue, it's a cultural attitude towards the concept of football: Spain likes it's technique and it's pretty football. There's also no debate that less bodily contact produces less wear-and-tear on players over the course of a season: it's physical fact. Therefore, by logical extension, Spanish clubs have significant advantages going into European competition, with a softer domestic league, especially if European officiating, again, favors less bodily contact. Therefore, an English or German European club title means significantly more than Spanish ones because they've endured more overall wear-and-tear through all competitions in a year. La Liga tarnishes Spanish club European success.