Octagonal cello bows such as this great student Primavera bow are often preferred by those who like a little bit of weight in their bow.
All violin, viola and cello bows infact start off octagonal, and the archetier (bow maker) will then keep some sticks octagonal, whilst rounding the others off.

There is no proven advantage or disadvantage to using an octagonal bow, it really comes down to personal preference, but octagonal bows will often be ever so slightly heavier than round stick bows.

This Primavera Octagonal Cello Bow is crafted from hardwood for the stick but includes a fine ebony frog as opposed to a cheaper rosewood or even plastic frog as still found on some entry-level bows.
Ebony is a delicate and impressive wood that feels comfortable to hold and is nicely weighted. A pearl-eye dot is featured along with nickel silver half-mounting, whilst the lapping on the stick is copper-nickel.

A popular choice with beginners and entry-level players in their mid-teens and above, this bow is available in all sizes to cater for cello's 4/4 (full-size) down to 1/10.