A n00b differs from a newb(ie) in the way of lacking knowledge, but not willing to learn from more experienced members and/or claiming his knowledge to be correct. They almost always type badly and use a form of SMS shorthand (lololz ur teh yri uzr!!) and perhaps l33tspeak, though a properly done latter is more rare.
"N00bs and newbies are very similar. However, there is one difference. N00bs generally ask before trying, whilst newbies try before asking, simple as that." -- Tratos, PPM