Always chamfer, especially after trimming. Though I only use a VLD chamfer tool because I like the less abrupt angle change and I feel like bullets start a bit easier.. The case mouths only usually need to be very softly worked with the chamfer tool to break any hard edge.

Also, I have found two other things in the process really, really help with consistency. The first is annealing. I anneal my "precision rifle" brass after every firing. Also, I use Hornady match grade dies, which utilizes a self centering neck size bushing that helps with concentricity and gives a much more consistent and tunable neck tension (I prefer right at 2thou neck tension for just about everything).