As for why the vord chose to attack Aricholt in the first place, simple. It's the most isolated. The Queen is nothing if not opportunistic. Perhaps she considered it a test run. Then, with her forces swollen with a new army of Taken, she picked a more central location as her base of power, from which she could be poised to attack any other steadholt with ease.
That's logical, and makes a lot of sense.
So here comes my however. (i was gonna write "my but" first, but rejected it as... aehm ok, where was i...)
They way it is now, it's not the most isolated. In fact of all the stedholts it's closest to Garrison... not an ideal target for a silent infiltration.
Ok now... Self! Stop nitpicking!
Self: No, i don't want to !!
Yes!! No Yes No Yes
In case i can't control myself in the future, let me repeat it once more.
The Map is great. I'm a nitpicking-casual-perfectionist... sometimes... and the map has me hooked in that regard.