Makari should be able to give you a more definitive answer, but I would say it would depend on what you take with them. Normally, one 5 ork unit of stormboyz isn't going to do you much good if you don't have the right things to support them, or if you are going for a mostly shooty army with them. Normally, I would say you would probably want to take either a 10 ork unit, or a couple of 5 ork units, and make sure you have the right support for them.
A tiny portion of humanity turned its back on mankind in the waning days of the last Golden Age. Over one and a half centuries later, the PHR has emerged from the shadows as an unrecognisable civilisation, its people irrevocably changed. They are no longer simple human beings, they are post-humans - cyborgs.