I like both, depending on their use. For sociability, the swivel are great. For writing or some other, more 'stationary' function, the stationary are it. The swivel is too much work to keep it stationary!

I personally prefer the white stools but both are nice and sit well within the room. If you prefer the black and they're sold out why not consider adding a chair at the end? I've only quickly messed around but why not add some accessories to the table? I'm not really a table runner person but there are some nice "scandi" style ones around which would add more texture. It's a nice room, hope you're making use of it :)

Depending on what colour your kitchen hardware is, there a couple of options that would work well in a graphite kitchen. If you have white worktops and a grey kitchen, I would add another colour or texture to the stools to create another layer to the scheme. If you don't like using bold colours, you could use an interesting textured metal or wood for the stools. You could try using something similar to the silver wire stools below for a more industrial style Or wooden stools are always lovely for a more contemporary country look. I would use a lighter wood, to add contrast to the dark grey kitchen and white worktop All the best with your project

The swivel ones usually have a lever that activates the gas that allows it to go up and down. The gas mechanism is usually within the middle pole. That way you can adjust the height. I have seen some that adjust the height by swivelling round, swivel one way the seat goes up and swivel the other way it goes down.