bb code..
i personally prefer html because you can also set height width etc of images.
also there is a "hidden" info about what tags are possible
(input format)
Allowed HTML tags: <h3> <h4> <h5> <h6> <em> <strong> <code> <del> <blockquote> <q> <sub> <p> <br> <pre> <ul> <ol> <li> <dl> <dt> <dd> <a> <b> <u> <i> <sup> <tt> <hr> <img>
h3-6 = header (bigger font) strong = b (big/fat) code = snippets of code
del = stroked tex sub = sub sup = supped text like ²³ etc
ul, ol, = lists , li = list element.. a = link u = underlined
i =kurisve , img = image well its not that hard but bb code would be more user friendly