I have a 10L Katadyn gravity feed for when I have the space, and it works great for multiple people in camp. I really like it.
I also often carry the MSR Hyperflow, which is pump-style filter, when I need to reduce weight / volume. The flow rate of this filter is very good IMO. The manufacturer does caution that you need to prevent the filter element from freezing (I keep in my 1-person tent with me, or if only using a tarp, in my bag).