HTML versus Wiki-makeup

I see that more and more people are use Wiki-makeup and removing HTML tags. But i like to use HTML-tags.

Is there, from a technical point of view any difference between the folowing notations;

= Foobar = (-> This does not seems to work) <h1>Foobar</h1>

== Foobar == <h2>Foobar</h2>

=== Foobar === <h3> Foobar </h3>

==== Foobar ==== <h4>Foobar</h4>

''Foobar'' <em>Foobar</em>

(and not:<i>Foobar</i>)

'''Foobar''' <strong>Foobar</strong>

(and not:<b>Foobar</b>)

'''''Foobar''''' <em><strong>Foobar</strong></em>

(and not:<i><b>Foobar</b></i>)

---- <hr>

Giskart