Patek’s World Time, in its various versions, has long been a favorite of mine. Certainly not the most technically complicated world time watch made, but I find the dial layout attractive and easy to read, and the time zone change mechanism is easy to use ...
You are so lucky to have 3 and enjoy them too. I had a YG 5130 Worldtimer, then went to a PG one, and then decided that my old eyes just can't see anything on the dial without glasses, so I sadly sold them. Cry! I agree, they aren't the most "complicated"...
I m also willing to aim for a trio of 5231(s)... One is there, 2nd is on order ... and 3rd let's wait and see ... Not rationnal to have 3 time the same watch indeed :p