The PS13 is the one without pop up headlights. PS13, S13, S14, S14A's are all great cars, just watch out as a LOT of them have really bad rust problems on them. Quite a few will have had it fixed in one way or another, just make sure one has.
The S13 came with a CA18 engine which many people like to bin for an SR20, but as above, the PS13 came with an SR20 as standard I believe.