It is quite impressive to see someone speak without notes. To be that good, you must either live or breathe your subject, which has a danger of making you less interesting, or you are well rehearsed, which is far more likely.
If you’ve got the time to rehearse, then do without notes. If not, use them, but note keywords only and refer to them quickly so you can return to facing your audience. Also, if you are using notes and get interrupted, it is much easier to return to your point. Without notes, interruptions can be tricky; saying “Now where was I?” could reduce your credibility.
There is some debate on the right format for your notes: A4 sheets, A5 writing paper or A6 index cards. Use what you find comfortable but fix them together. If you’ve ever seen a nervous speaker drop their notes and then try to put them back in order, you will know what real chaos is.