I would consider AAC support to be much more marketable than ogg. The iPod has a huge chunk of the MP3 player market, and winning that market long-term means getting iPod users over to Sansa. iPod users pretty much have to use iTunes, and the default iTunes encoder (for ripping CDs) is AAC. Consequently, many iPod users have large AAC libraries. iTunes (by far the largest reseller of legal music downloads) also sells some albums in unencrypted AAC, which works on a Zune (and others) but not on a Sansa. A lot more music is also showing up on the (illegal) download sites in AAC format. The Ogg user base is very vocal but still relatively small.
I went from an iPod to a Sansa, and I have to say one of the big drawbacks is the lack of AAC support. Even my car stereo and DVD player support AAC. None of them support Ogg.
