6" I do split in half. I have a three-year shed, so I shouldn't need to, but I like a flat face on my firewood. Allows me to pack it tighter in the stove and thus achieve longer burns.
It is true that you can do small fires in a big stove but not the the reverse...
If you can hold off, get enough wood split and stacked for two years out now (as in before May or so), and get a modern stove in two years, that'd work. Modern stoves do not do well with wood that's wetter. Your older one will keep you warm in the mean time, and you'll be much happier with the new stove.
(And then next year, cut split stack only the quantity needed for the one season two years after.)
Slab cut offs are the same as splits regarding drying characteristics, imo, but others may have better things to say there.
It is true that you can do small fires in a big stove but not the the reverse...
If you can hold off, get enough wood split and stacked for two years out now (as in before May or so), and get a modern stove in two years, that'd work. Modern stoves do not do well with wood that's wetter. Your older one will keep you warm in the mean time, and you'll be much happier with the new stove.
(And then next year, cut split stack only the quantity needed for the one season two years after.)
Slab cut offs are the same as splits regarding drying characteristics, imo, but others may have better things to say there.