The overall size of the handle, which includes both length and thickness, is a much overlooked attribute when initially selecting a shaving brush to suit you.
For example, small hands are probably more comfortable with a smaller handle. Likewise, big hands -> big handles. But of course we are all individuals and those rules don't always equate.
You can't go horribly wrong with your choice, but in time and with some experimentation you'll find a length you really like.
Brush Handle Size, Knot Diameter & Loft Size. These details can be found on each product page.