I thought the same thing, but the ambulance guy when he fitted the capsule said that the side was safer
I've got the meridian car seat - and it's situated in the centre of my car. I've got a commodore - so there is plenty of room. But when I went to have it installed I phoned Safe N Sound and asked them the best position. They said the CENTRE as a lot of accidents are t-bones - and the centre is the furthest away from any impact. They say a lot of people put the seats on the sides for their convenience... not the baby's safety.
But they did say that if you have a 2nd child, you have no choice but to put them on the sides...

Because the car seat is strapped in/down from the back part... I don't know how much difference a raised seat would be?