Well if it is simplicity or ease of reading, either the HT of the Master Geo would be a good choice over the Master World. The Master World Geo seems to me the only world timer of the three since you can see all the cities/timezones at once, but I can see that being the hardest to read quickly, even though I share Nicolas' passion for worldtimers.
I am partial to the Master Geo because it is the easiest in terms of selecting the city you are visiting. The placement of the second time zone subdial is located right above the selected travel city and there is an indicator right there to the left of the subdial to tell you whether it is pm or am, which also allows you to read the time in the visited city in either 12-hour or 24-hour format. It is incredibly clever, easy to read and intuitive. And as emcquillan mentioned above, the Master Geo is the only model that offers day/night indication in both time zones, which is nifty. I am very taken with the Master Compressor Geographic, the sporty version of the Master Geographic -- it was my first JLC love, but certainly not as dressy as the ones you are considering.
One other thing to consider is the power reserve indicator. Do you like it or not? Again, personal preference.
Both the HT and Master Geo are ideal and true travel watches, so you can't go wrong. You will decide on which one speaks to you more. All three are beautiful.
Looking forward to seeing what you choose. Good luck.
respo