Thanks for writing in! I'm going to assume you're asking about shutters (as pictured in this photo) rather than blinds (which are raised and lowered usually with a cord and aren't made in a 3 1/2" size).

For a window that's 72" wide, we'd generally recommend a shutter with a wider louver (3 1/2" or even 4 1/2") as you get more light and better view-through with the wider louvers. The wood composite material has a nicer, richer look and feel than the vinyl, but it's also heavier and therefore more likely to sag in a window that size.

If the window is 72" in height, you might consider the smaller louver and the more attractive wood composite if the width of the window isn't terribly large. Hope that helps! Let us know if you have more questions....