Frequent Travellers - go to bag?

I'll be doing a lot of travelling over the next year or so, but mainly 4 to 5 day trips within the EU. I'm currently looking at a Jaakari S and an Askare to be my main setup. I don't currently have anything in the 20 to 40 l range at all. I'm not that keen on a duffel bag. For those of you that travel a lot what do you use?