Can your roller suitcase handle rough sidewalks, etc.? If so, you may find it easier than carrying a backpack. I had a large roller duffel with me for my 8 week trip, no problem. Either one should work fine, though. Argentine taxis are a real bargain, so doubt you will have to walk terribly far. I guess for 5 days I might echo Hiddy's comment about feeling more "adventurous" with the backpack. Have fun!