I'll not get in to the order you should upgrade things, as that can be a personal thing - for instance, if you love the feel of the stock trigger, no point in telling you to upgrade the trigger; if your loader happends to fit the stock feed neck perfectly, no point in telling you how great a lever clamping feed neck is. You get the idea.
As far as the boards a re concerned however, the Hater board offers more adjustments and more firing modes - it is the better board without doubt. However, having said that, you need to decide whether you need those extras, as some people find the Blackheart perfectly adequate, and that it offers all they really need. If there is a price difference between the two (as there normally would be), some people would rather pay less for a board that only does what they need it to, rather than to pay extra for a board that does things they will never use.
I'd be happy to pay extra for the more versatile board, even if I don't use every feature - you need to make that decision for yourself.