Steve Jones looks at a pair of procedures:
I was creating a question on sp_readerrorlog and realized that this procedure is different from the one it wraps: xp_readerrorlog. This post digs into a few differences.
Click through for the answer, though Steve’s reference of sp_readerrorlog being “new” is, I think, not quite right. I’m pretty sure that both sp_readerrorlog and xp_readerrorlog were introduced in SQL Server 2005. I did dig up a Rodney Landrum article from April of 2010 talking about sp_readerrorlog, so it was at least in SQL Server 2008.