What is the main advantage of a 501(c) organization over a 527 organization?

A 501(c) organization is a group that
is allowed to claim non-profit and tax-exempt status. Simply put, this allows the group
to receive and spend donation without worrying about paying taxes. Many different types
of 501(c) groups exist; at the moment there are 28 subcategories: 501(c)(1) through
501(c)(28). They perform hundreds of different functions, including charity, religious
work, advocacy, public service, private service, medical research, and technological
experimentation.

A 527 organization,
while still tax-exempt, is created specifically to advocate for or against a political
candidate. 527s do not self-identify with any political party or figure, and so avoid
taxation under the Federal Election commission, or the contribution limits places on
Political Action Committees. Their function is to raise awareness and inform the public
about little-known facts, and influence the eventual
election.

The main advantage a 501(c) has over a 527 is
that it can be formed for almost any purpose. While a 527 is limited in the ways it can
spend money and cannot outright endorse a political figure, a 501(c) is not bound by the
same rules in its pursuits. However, many 501(c) organizations
cannot engage in political action; 501(c)(3)s are specifically
prohibited from such. In contrast, 501(c)(4) and 501(c)(6) organizations are allowed to
lobby and advertise in favor of specific political policies and
figures.

To reduce the issue to its essentials, remember
that a 527 has little other purpose than to advocate politically, while a 501(c) may use
its main purpose -- for example, raising awareness about environmental concerns -- to
nudge thinking towards their chosen candidate as long as they do not engage in any overt
political activity.