My go to supplier is geterbrewed. Their quality and service is spot on. For me, the advantage is that they sell hops in 50g too. I don't always want 100g, especially if they're not American. I don't have any means of resealing them, so can't keep opened packets for long. They also sell grains in 500g quantities if needed and up until recently you could get 250g. Not sure how this compares to other suppliers. That said, I've used the Maltmiller for bits that geterbrewed don't sell and their service and quality has been great too, but the range and hop options just edges geterbrewed for me.
Good points there. I would like to able to get 500g packs of malt and 50g hops from MM. It has caused me to use HBC a lot in the past. MM, HBC and Geterbrewed all have their strong points, always a tricky decision!