1) If they're only using on disk indices, it'll be slower to look up any one record than it would be if the index was in memory (particularly true if a good chu

1) If they're only using on disk indices, it'll be slower to look up any one record than it would be if the index was in memory (particularly true if a good chunk of the data was in memory also) 2) The operation of retrieving a full row of data is more expensive in a column based db than in a row based db, because in row based the data for the row is contiguous on disk. So row based is likely optimal if your data size works with that architecture. (And, to be clear, row based _can_ work with billions of rows, if you're thoughtful about what kind of querying you'll be doing against such tables, and how you maintain them.)