I usually check in a bag for all the sorts of reasons LTN Phobia mentioned.

Then my carryon is usually a Karrimor Kodiak 35 rucksack, as c-w-s mentioned the size of soft, non-wheeled carry-on bags is rarely questioned. The Kodiak is not made any more but I have three stored at home and since the service life in daily use by me seems to be 2-3 years, I will be fine for some time.

However, sometimes I do carry on another bag. For luggage that may go in the hold, I use only Eagle Creek. My smaller bag is the Load Warrior 22, which meets BA (and most other) size limits and is significantly lighter than the Rimowa. They last me for several years.