The difference in cost between the rolling duffel and the carry on is the ability to carry on vs checking the duffel I think. That rolling duffel looks sweet but when investing in luggage you’re going to want to get a bag that has multiple purposes and if you font have a good carry on solution, I would go that route.
I used to use whatever old luggage I could grab from a family member or friend back in the day but as my travel ramped up, investing in a few quality pieces made it so much easier without worries of a zipper breaking or a wheel falling off in the terminal.