Thanks for the replies. I was just curious.
Personally, I don't store a huge amount of media on either device but my breakdown is like this:
My iPhone 6 is my music player, with all of my music stored locally. My iPad Mini 4 has almost no music except for a few songs that I use for specific occasions like my alarm. Movies/TV if any, are on my iPad. Rather than storing a large library, I just put stuff on as I need it and remove it once I've watched it. Photos are the one thing that I sync between devices via photo stream, since like most people I prefer taking pictures with my phone rather than tablet, but I like being able to view them on the larger screen later.
Both of my devices are 64GB, which is sufficient for my current needs.