OR or IN ? - Mailing list pgsql-general

Hi all,
I've got a query with a long (>50) list of ORs, like the following:

SELECT colB, colC FROM table WHERE colA=X OR colA=Y OR colA=Z OR ....

Is there any difference in how postgresql manages the above query and the
following one?

SELECT colB, colC FROM table WHERE colA IN (X,Y,Z,...)

Which is the suggested index to use on colA to get better performances?

Thanks,
Luca