Filter before the pump has worked for me. My pump is about 2 ft past the BH filter.
Overall, I've been happy with the hop filter. At first I had the beer flow going inside the filter...basically backwards. Also, my best results have been keeping the device vertical. The pics on the BH website are helpful.
Like many things in brewing, there are a lot of variables for effectively reducing hops/trub/other. My preference is to whirlpool, use mesh pickup tube and the BH filter. When using whole hops I'll use a hop chute (stainless tube similar to a spider).