clare,
What would influence your decision?
It has just been a culmination of my experience over about ten years.
I started with WBCs and Nationals. Jumbos were hardly heard of, but 'brood and a half' was often used. I used 'a super-over for wintering' after my second winter, for sure.
After my initial start, when I stripped out as much honey as I could and replaced it with sugar (following the crowd in my first year), I found that I was left with some frames with 'dubious' honey in them. So I soon adopted the 'leave a super' and only top up if necessary approach - I also had some honey surplus that was a 'buffer' for a poor season. Those years were steadily getting warmer and the bees generally collected enough late in the season such that a few frames, kept back from harvest, could be slotted in where any short-fall occurred. I actually found myself finishing up with an extra super, or more, to be extracted very late in the season. In effect I had changed my philosophy from 'harvest as much honey as possible' to a more 'just take the surplus'.
While this was going on I had bought my first 14 x 12 and liked it, mostly. I also tried one (or two) hives with the new idea of an OMF. I also changed at that point and went to top bee space.
All this in about 4 years! Some of my friends in the LBKA were frowning at all these changes, and muttering that 'I would still finish up on the same kit as everyone else, when I stopped making so many changes'.
The final outcome was a dry hive (no damp or mould on outermost frames in spring) with enough stores in the one box. That is what I have used up to now. The Dartingtons fell into the collection purely as a 'try-out' of the system (as did the Beehaus).
Only 11 or 12 frames to check (except that I still allow her to lay in a super as well, as there is still often insufficient brooding space at peak spring build-up), no winter top ventilation at all, all supers were always 'proper honey' (I hoped), WBCs were definitely too small (IMO) for the modern bee (yes, I had swarming problems early on!) and so, too, were my standard Nationals. Home-made ekes were cheap and easy to convert from standard to Jumbo. Generally bigger colonies seem to allay fears of wasp attack - I still get them, but even late splits of a full 14 x 12 are generally fairly 'wasp resistant'. Just one full frame of hatching brood, moved to a weak colony, is one h*ll of an increase for the receiving colony. 14 x 12 nucs are more easily maintained (one full frame of stores is enough for some time). The brood nest can closely retain it's 'ideal' shape (spherical).
Downsides were: Weight, which at that time did not unduly bother me. Getting the large format frames drawn satisfactorily (not so much a problem when spare drawn frames are available). Leaving rather more honey from the crop (I am only a hobbyist, so that is not so important - and running an 'extra hive' was simple compensation for that one - and I don't count the number of honey jars filled by each colony each year!). Different format to the rest of the local BKA members - I couldn't help the locals out with a test frame, for instance. Possibly locating the queen, although that is now not really a problem - and I rarely search for her anyway.
So my recommendation for your colony is simply for it to be of similar dimensions to the system which works admirably for me.
I find the 14 x 12 is a good all-round size. For instance this year I recovered a swarm and housed it in a 14 x 12 nuc with undrawn foundation, left it over-night in a warm place (the hall in my house!), transferred it to a full 14 x12 brood, in a new location, with more undrawn foundation and the box was completely filled in, I think, 3 weeks. Totally filled with brood and stores. A complete up-and-running new colony in less than a month with minimal input from me, with her laying upstairs before the month-end as the new brood was only just beginning to emerge (for more laying space).
Others have other ideas and ideals. I have found the above worked for me and gives me less worries over the winter. I have done my bit and if they don't survive, it was beyond my control. There are other combinations for over-wintering, I know, but 'hefting' from Chistmas onwards, is not for me - I know they will have enough until brooding starts in earnest - until about late Feb.
Your experience will eventually guide you into your most liked method. I found 1) more stores were better than marginal store levels, 2) ventilation was paramount (and 'bottom only' was good, via the OMF, for me) - I did not master the regulation required for top ventilating in about 4 or 5 years, 3) good top insulation helps a bundle and 4) no space should left unfilled above the cluster.
If nothing else, the above will give you something to think about!
Regards, RAB