In general, is direct query faster than a view?

[Alan Myers]

Just a general question. I'm wondering if it's CRAZY to build view that groups data when I can just do my own count:

So, for example, a simple count. (There's an index on id):
SELECT count(1) from largeTable where id=100

Is there huge overhead to create a view as:
CREATE VIEW myView AS
SELECT a.id as id, count(b.id) as num
from smallTable a left join largeTable b on (a.id=b.id)
group by a.id

and then pulling data from the view:
SELECT num from myView where id = 100

As long as I don't call the view without a where clause, are they equivalent?