The only advantage is that Foradil has a faster onset of action.

Serevent takes about 30 minutes to start working so when it is
prescribed patients need to have a faster acting "rescue" medication
(usually albuterol) and instructions on which to use when.

Foradil has an onset of action within minutes. Its official labelling
calls for the same cautions and concomitant prescription of a short
acting med as Serevent but some people question whether the onset of
action is fast enough to use as a rescue. Albuterol is certainly
faster so if someone did use Foradil in this manner they would need to
be instructed to wait several minutes before taking a second dose and
not expect the relief to come as fast but this is not all that
different than what you get when you use a neb which takes several
minutes to complete.

Where I have really heard this mentioned is in the context of
discussing the combo Foradil and inhaled steroid. If you give this
product and have people use it as a rescue inhaler as well as a
maintenance med you would decrease the number of prescriptions and
automatically titrate the inhaled steroid up when the asthma worsens.
It would kind of become its own self governing action plan.

Of course, some studies should be done before this is widely
recommended and I have not seen anything on this in writing from any
kind of major organization but it is what some specialists are
discussing off the record.