Because they were capped at different times. Availability might've dictated something different. Or perhaps that year they altered their bottling practices. Or maybe someone has drunk it, replaced it with their urine blended with beetroot juice and recapped it...
Oh god, this is like the wine equivalent of PC vs. Mac
PCs are better obviously.
Corks can dry, fail, leave bits in, etc. Caps are normally a better seal.
There's probably some argument for corks - tradition, some other shit I can't remember. Google for discussions about each option's merits.
Because they were capped at different times. Availability might've dictated something different. Or perhaps that year they altered their bottling practices. Or maybe someone has drunk it, replaced it with their urine blended with beetroot juice and recapped it...