The simultanious play option is anything but 'real time'.
The two are completely different.
In the simult. play option moves are plotted by all players and then they are all executed at the same time. It can make for a much more 'realistic' feel sometimes.
For example, take a fast 'scout' and try to catch him with a slow battle cruiser and in IGOUGO turn based it is a black and white issue. Either you have the MPs to reach him this turn or not... BUT in simultanious movement you don't know, it all depends on the move of the scout. If he 'runs' you will never catch him. And that, IMO can be much more 'realistic'.
Give it a try, 'real-time' it is NOT.
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The Grumbling Grognard