Asia's bonus is quite beastly if you want to use S.H.I.V.s and more importantly, to get through the Officer's training school quicker. Getting all the upgrades fast is amazing and it frees you up to go for money making missions more often. Also, there is nothing stopping you from getting Africa next once you get your satellite fleet up and running. I would highly recommend going for one or the other and then immediately pursuing the one you didn't choose.
But really, the only bad choice/hard mode choice is south america. What a lame bonus when compared to everyone else.
Without spoiling anything, you run into some late game enemies that are just a bunch of jerks who just want to ruin your day with their mile long health bars. And when you are running with a bunch of colonels or near ones, you are not going to be taking as many risks in trying to face these enemies head on. The solution? Soften those jerks up with your own robotic death machine. Human ingenuity at its finest. This is especially so when you have your upgraded hover S.H.I.V. s with plasma weaponry. Pew Pew.