Personally from playing civ rev a bunch before getting into cIV i would go against simultaneous turns. It may be different because of a 24hr turn period vs a couple of min but there can be issues where both people move at the same time but one gets to move fist then the other attacks them even though they probably wouldnt want to attack someone on a forested tree hill.
Also people often wait til the very end of turns to move their boats and drop them off next to the city and attack at the very begining of the next turn. leaving out any hey a bung of tanks landed next to my city should i send defenses there decision making.