Alessandro, I have never used El Greco Inks so can't comment on them.
I have however used Stormtroopers Inks for many years, both standard inks and the newer mixed Inks.
I can only say that these are super inks and always seem to do the job with no problem.
Only problem you will have with either would be the amazing covering power that they have. A very tiny drop goes a long long way as I have found to my horror. If you have a brush for Printers Ink, never ever use it for anything else no matter when you last used it for ink.
Hope this helps.
Don