Octa or Square/Rectangular Softbox...what's the difference?

Other than the shape, obviously. It seems to me that a square softbox would be easier to control the light spill than an octa, but maybe I'm way off base. Does it just come down to personal preference? I'm about to pull the trigger on a 24inch square softbox with a grid but then saw that I could get a bigger octa softbox for just about the same price so it got me thinking....what really is the difference and what are the pros and cons to them.

Anybody have any insight? Thanks!

The biggest difference is the shape. Some people like round (octagonal) catch lights. Others like square/retangular (Window shaped) catch lights. Both can be controlled via grids. What is much more important consideration is size relative to your intended subject(s).

A 30" modifier, 30" from the subject will provide the same wrap as a 48" modifier 48" from the subject. As the modifier gets smaller relative to the subject there is less wrap.

So it essentially boils down to personal preference?

Yes.