For me, it's mostly a matter of curiosity, as DQ VI is the last of the mainstream DQ games to appear on Western shores. Like DQ IX, it employs a job/class system, but unlike DQ IX, it does have established characters. The latter of these facts lets me know that I'll probably enjoy it more.
I would never recommend that play more than one DQ game in quick succession, but I've never found myself getting bored with any of the DS entries. IV, V and IX have a lot of similarities, yes, but the structure differences are subtle enough that I would hesitate to dismiss them all as being iterations of the same game.