An interesting and somewhat illuminating thread! I chuckled a little about the discussion on fares : our first cruise with P&O was several years ago and we had paid what I thought was a really good price (still do if I'm honest) but we'd barely set foot on the ship when a very strange woman rushed up to us, asked us how much we had paid and before I could even think of a polite reply, she told us what she'd paid - it was over £100 pp less than what we'd paid!!!
But why Cunard? Simple really - we enjoy every aspect of every sailing, from the formal nights, the guest speakers, entertainment, food, etc etc. We've sailed on other lines, on the mega ships and have also enjoyed them, but with Cunard there is that almost tangible something extra that draws us back time and time again.
BTW, we once followed up a crossing with a short cruise on the NCL Breakaway and when I asked for info on the ship (on CC forum) some people were absolutely horrified that as senior citizens who sail Cunard we would be on a 'fun' ship and some even went as far enough as to suggest that we changed to a smaller and quieter NCL ship!!! Needless to say, we didn't and actually had a great time. DH was particularly taken by a young lady who came into the MDR one night wearing the shortest pair of shorts we've ever seen!! Now that would never happen on a Cunard ship.