Assuming you're talking about the schematic symbols:
I personally prefer to use the rectangle for ICs that have no internal structure visible on the schematic (only pins).
For components like relays where there's internal detail, the rectangle looks weird because the internals have to be drawn with a polyline which have rounded edges. So I draw the rectangle around it with a polyline too.
As far as actually using the components on a schematic, it makes no difference to CS.
You can always browse the vault and see how similar components were drawn.