This is indeed an interesting question. The article Ultimate Mobile OS Showdown: iPhone vs Android vs webOs vs Blackberry vs Windows Mobile vs Symbian tries to compare the good and bad of each of the common mobile OS at hand today.WorldMate is mentioned in this article as one of the better BlackBerry OS third-part apps for tracking travel plans.
Personally, I like the Windows Mobile OS, but I have to agree this is probably a dying mobile OS.
iPhone is very chick but if I have to gamble on a winner it will be the Android. Its openness and support from a plethora of vendors will make it the winner, eventually.
What do you think?