I use a backpack as my personal item because it's easy to carry when in the airport or getting to or from the airport - and it doubles as my daily bag for work or pleasure at the destination. I find backpacks easier in general than shoulder bags / tote bags that rely on one shoulder strap or which need to be carried by handles in the hand, for daily carry.

This is for times when I am not traveling with just a backpack and no personal item instead of a rollaboard, of course.