Given that the N64 was released in the North America in September 1996 and that the first stable release of Vorbis wasn't released until May 2000, it's very probable that OP couldn't have considered/used Vorbis.
It was probably 1999 that I wrote the first version. Ogg was still in development at that point. I know I considered a few codecs but mp3 was relatively well supported with 'reference' codecs.
Oh, ok. I thought "few years" was meaning actually few years. Did not know much about N64. After googling, it seems devs were still active in 2003-2005.
Mp3 was the only option that was relatively mature and had good enough compression ratios for what we needed (as I remember). Anything more computationally expensive was completely off the table.
