I think most consider WR a top tier maker - I certainly do. What adds to their popularity is, I think, their guns seem more accessible to mortals.
I don't see much reference in the literature of a PH having Purdey or Holland send out a rifle to Mombasa for them to collect at the end of a long safari. Seems like WR, like Jeffrey, was more of a working gun maker intended for real hunters in the know, and the Purdeys and Hollands were more likely to be sold to their wealthy clients.
Maybe this is just my perception. For me, a good Westley Richards is more desirable than a Purdey or an H&H.