Rat catchers tell us, and my own experience backs it up, that deterrents (along with removing the sources of attraction and the means of ingress) are helpful in stopping rats from taking up residence. But that if there is already a problem, deterrents will have pretty much no impact. First of all, the current incumbents have to be removed. Poison or terriers, or terriers followed by poison, are the only ways that seem to work once there is an active infestation. (And believe me, I have tried so many alternatives over the years! I hate having to use poison, but I have grudgingly accepted that it's necessary once the rats have moved in.)
Then, once there is no longer a resident rat population, the deterrents (coupled with sealing holes and removing all attractors of course) may help to reduce the likelihood of, or at least delay, another lot moving in.
Anyway, that's my experience. Just thought I'd share it; you will make your own mind up of course. (Everyone told me the same and I had to find out the truth of it for myself... I think most people do, no-one likes having to use poison!)