Best fragmentation strategy

I have an opportunity to change the fragmentation strategy on some heavily used tables. Most records on these tables are only accessed on the day they are written. They are written, read, and updated only once or twice. Also keep in mind that we are on a SAN, so I have no control over where the data is physically stored. So my question is... is it better to have a different partition for each day of the month ( only one partition at a time is being heavily accessed) or to use round robin to theoretically 'spread out' the storage access across more of the disk. Thanks in advance for your opinions Laurie