I have never heard of Graphotech, but Olympos I have heard of.
The Olympos I believe are made in the same factory with Iwata so they are very similar to Iwata's quality.
Sorry I can't help you out more as these brands are not real common in the U.S.
Mike
“Wisdom is the right use of knowledge. To know is not
to be wise. Many men know a great deal, and are all the greater fools
for it. There is no fool so great a fool as a knowing fool. But to know
how to use knowledge is to have wisdom. " Charles Spurgeon