I'd say buns because they really can be done by just about anyone. Wigs are great too, but not all women like the idea of wigs or "fake" hair. The bun, tucked pony, or loose updo is a unversal and easy style that can be dressed up or down.
For me, both wigs and buns are abt equal in terms of which I use (I use wigs Sept-Feb, and buns or loose twisted updos the rest of the year when it's too warm here for wigs IMO (Mar-Aug)--I can't stand sweating under a wig, but some ladies wear 'em year 'round in the South no prob. This hair is too thick...even when braided down, I just CAN'T do the wigs in summer.
Right now I'm in a the "grow out" phase, otherwise I could use my hair sticks to secure my buns instead of ouchless elastics...[SIGH] can't wait til I'm at least BSL. I also love braids w/extensions as a PS, but the install and takedown time deter me from getting them too often.