or when sliding a box back into position. i.e. less headless bees.
That not enough? That affects speed/ease of operation, of course.
I use and prefer top space. The most used format in the world (Langstroth) uses top bee space. The UK is out of kilter with the rest of the world?
Crown boards are simple boards - cost saving. Winter insulation sits absolutely flat, without any problem.
Can't so easily use floppy Queen excluders on top bee space (may be a cost downside to those with floppy Q/Es already) and framed Q/Es are the far better/easier choice. I use framed wire Q/Es (when I use them), so not now a problem to me as the few slotted steel are eventually destined for some other use or disposal.
Need to avoid sitting boxes on solid flat structures (frames can be pushed upwards slightly). Not a real problem for most beekeepers.
Not compatible with the users of bottom bee space boxes. Not a problem unless swapping/borrowing/lending boxes, which is not good practice, but sometimes necessary for some, it seems (usually new beeks) and can be 'got around'.
Don't have Q/Es glued down to frame top bars with top bee space.
Yes, I prefer top bee space.