Sequences and inheritance

If I have a set of tables and I set their primary keys all to the same
sequence, as in

create sequence common_seq;

create table alpha (
ID integer primary key default nextval('common_seq),
other_field text
);

create table beta (
ID integer primary key default nextval('common_seq),
other_field real
);
create table gamma (
ID integer primary key default nextval('common_seq),
other_field oid
);

Would this guarantee that each value of ID in any row of any of the
tables would be unique amongst all of them?

Would I get the same effect by creating a table like this:

create table common (
ID serial primary key
);

and then having alpha, beta and gamma inherit from it?

--

Bruce