my original hive went bonkers this year.....from all the info around here I think I'm gonna try a double brood next year
Good decision, Nick, because it's a simple upgrade that will give you flexibility.
When you say
bonkers, I guess you mean prolific. This is routine for modern queens - Carniolan and Buckfast make big colonies of good-tempered bees and are sold to many beginners.
My take on this hive conundrum (having run 14x12 and National deeps) is that hive flexibility (and not size) is crucial to responsive seasonal management. Compare a hive to an accordion: both should be capable of rapid vertical or horizontal expansion and contraction.
In this respect a set of smaller boxes answers well; at the other end of the scale, a vast Dadant or Langstroth Jumbo would give enough space, and could be dummied to give internal flexibility.
What I would avoid is brood+half and 14x12: the first because it gives twice the work of a single box but only half the space advantage of double brood, and the second because the 41% extra brood space a 14x12 gives over a National deep is not aways enough (and then where do you go?).
If you want a really simple life, imagine using one size of box throughout: I work for a honey company that uses only brood boxes and no QX. Swarm reduction is significant. As the season progresses the top boxes are back-filled with honey and the colonies over-winter on two.
My system is similar in that I aim to have colonies on triple National deeps by May, but with QXs and supers on top; Ian runs his similarly and confirmed what I find: by late summer the bottom box holds a lot of pollen, the nest is (mainly) in the second, and honey rammed in the top BB and supers.
Granted, full National deeps are not light, but lift them properly and it's no big deal.