Bands stay in better than barrettes and are safer since a barrette can be a choking hazard. The bands on the bow are for placement only so it is very easy to pop the bow on after you've made a topknot.
If you prefer the ease of a barrette, make the topknot first, then clip the bow directly under the band so it can't slide up. A barrette can be clipped on as an accent without a topknot, but remember not to put too much hair in it or the release bar will pop off and the barrette will be broken.
This is my favorite topknot tutorial:
Topknots shared by Linda Grimm and Maria Lelinho starring Rocky! Many Thanks!