It seems that 世論 can be pronounced as both よろん and せろん. Are the meanings identical? Is one pronunciation more common than the other?
1 Answer
Practically, Eddie Kal's comment is right: you can use both (no change for nuance) and よろん is more common (see 5. 言葉の発音).
Historically, 世論 was せろん and 輿論 was よろん. Since 輿 was not included in 当用漢字 (1946), 世論 came to be used for both readings (cf. Wikipedia article for 輿論). The linked article says 世論/輿論 meant different things up to Taisho era, but the difference is lost now.