I use the 5k. I have no reason for choosing it over the 3k though. I've actually thought about picking up a 3k on the theory that 1 lap on the 3k = more than 1 lap on the 5k. But then I thought about it and decided not to go that route.
The 5k feels very soft, but removes metal pretty quickly. I've only used it as part of progressions on antique store finds, which means very, very dull razors. I haven't found the 5k stage to be particularly slow, assuming I've set a decent bevel.
I have full set I used the norton 4k 8k so i was looking for the same set up with naniwas
I got the 1k 3k 5k 8k 12k I would say the 3k cuts like the 4k norton and the 5k is like the 8k norton i have shaved of 8k naniwa with no probs at all .I agree with chap above the 5k is a nice stone that cuts slow but also polishes I'd get 3000/8000 combo 12k finisher lynn uses them and he says you can 3k to 8k or 5k 8k it doesnt matter although after 1k he did go 5k 8k i go 1k 3k 5k 8k 12k it works the choice is yours
I had both. The naniwa super 3k single in 10mm in the early days.
I sold it because it was too soft for me,
as I like to sharpen kitchen knives as well.
It´s feel is very, very buttery. At least it was for me.
Way more buttery than the 8k, wich I think is just perfect.
Last week I bought an Naniwa Super 2k/5k kombination stone
(those are sold here in europe, as well as a 3k/10k and 0.8k/5k and 3k/8k ^^ !)
I like the 5k better then what I can recall from the 3k.
It can be used directly after the 1k and there is no big jump to 8k
(3k->8k wouldn´t be a problem, though !)
The 5k feels harder and more reliable. But still, nothing beets the supernice ss8k
You can go and just buy the one you like best. Both will work,
but it seems to be most prefer the 5k due to personal preferences