...which is that you would like to see both time zones immediately. That's the way that I like it as well, which is why I am strongly drawn to the JLC Geo and Lange 1 Time Zone rather than to the PP (or now VC) style world timers, which are not at all intuitive to me. The VC Overseas Dual time is built on the same concept, although to me a bit less useful due to the absence of a minutes hand on the second time zone.
I also own a UN dual time, but for whatever reason find the display of the hour in the little window less useful.
If you don't need to see both time zones exactly at once, the Reverso Duo/GMT watches are really cool -- two time zones on different sides of the watch, with two entirely different faces. An under-appreciated complication, IMHO.
Have fun choosing, and tell us where you land!
Best,
Gary G