Simultaneous is also great for setting up long order chains and if you make a mistake you can just clear the orders and start over, so you don't waste a turn.
I always used to play in Sim mode in SE IV, but with SEV it's way too tedious. Camera is reset after every turn, you have to 'login' after every turn, turn processing takes much longer because it 'reloads' the game *two times*( before and after the 'processing turns') for each end turn sequence, etc.
Yeah, it could do without the reloading, but that shouldn't have anything to do with simultaneous vs turn-based... I haven't tested it but it seems like the two shouldn't be connected.