For a fishing trip I took back in January, I used a 125L Fishpond Stormshadow large rolling duffel. Argentina allows NO fishing tackle of any type as carry-on luggage on domestic flights. I would have been OK flying into and out of Buenos Aires, but we also had a domestic flight to/from Esquel. So, I had to carry all fishing gear in a checked bag.
As a result, what I needed most was a bag long enough to accommodate four-piece fly rods, in addition to carrying everything else tackle-related. Fishpond designed the bag to be able to fit their Dakota rod/reel case inside, which is what I did. The Dakota case adds an added measure of protection for the rods (no tubes) in the checked bag, but I really wanted to bring it along to use as a means to organize and transport rods/reels in the guide's truck on a daily basis, and it worked out very well in that regard. I was able to squeeze seven 9' rods in the Dakota case. Also, I brought a waterproof backpack as my personal item.
My son traveled with a 100L Osprey rolling duffel, which he had prior to planning the trip, but it was juuuust short of being able to fit a four-piece rod, so I packed all our rods in my bag. It would be nice if his bag was a few inches longer.
My understanding is that there may be other countries in addition to Argentina that do not allow fishing tackle in carry-on bags. If so, you may want to consider a bag long/large enough to accommodate rods just in case you travel to such a place in the future and need to check the bag.
Here are a few pics of the Fishpond Dakota inside the double-sided Fishpond rolling duffel. I took the pics and saved them on my phone along with a list of items so I could use it as a cheat sheet for any future travel. I packed most all of my clothes in a carry-on bag. After this experience, I could likely find a way to pare down some things, but you might be surprised how quickly even 125L of volume gets eaten up with gear such as waders, boots, heavy wading jackets, fly boxes, etc.
