can i get some advice on carryon luggage?

this summer i am going out of the country for two weeks. well, decided i that i am only going to take one piece of luggage, and that peice of luggage would be a carryon. currently i am leaning more towards the big comfortable backpack approach, however i was also thinking of a nice hardside peice of luggage. i realize that each airline is different on what is acceptable for carryon luggage. in your experience which is better? anyone have a preffered brand?

I went during the end of this past year and took 1 backpack type carryon.

However, I packed to nylon duffles into it so at the end when I had a few presents I had extra room.

Also, the duffle came in handy for day trips. I.e. carrying my camera, map, water, etc.

International Traveler Animal Print 3-piece Hardside Lug…

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