The fact is, the S”A (I think it’s the S”A) says it best- echad hamarbeh ve’echad hamamit, rak sheyechavein libo lashamayim-
It’s not the Mechaber, who holds to drink a lot, it’s the R’ma, who seems to be legitimizing both shittos (which is why Sam’s chiddush in the p’tur in hezek is wrong, IMO)
http://hebrewbooks.org/pdfpager.aspx?req=14166&st=&pgnum=323
Hence it is a chumrah.
It is a chumrah in Hilchos Purim, but a kulah in Hilchos Deios.