There isn't a right or wrong. It depends on the design of your cabinets and your own taste. I'd tend to do vertical, but I think that's because I'm accustomed to that, not that it looks objectively better.

Whichever way you go, get lock nuts or something or you'll spend your life adjusting them.

My gut says vertical on doors and horizontal on drawers, which probably is no help.

Oh, you know what, I just realized that my gut is saying that because that's how the pulls are in our kitchen. Vertical on doors and horiz on drawers. It doesn't look as stupid as it sounds with our pulls, but it might look a little off to have rectangular knobs turned different ways.

My advice, then, is that either way should be fine and you can go with your gut too. In my house knobs shaped like that would probably be every which way, including various degrees of diagonal, within a couple of weeks; so round would work better for us. But your knobs are very nice indeed, so no need to listen to me. :)

I kind of agree with northcarolina
Initially, I thought horizontal but than in my usual pattern of overthinking.....

Those are the same knobs that I have and they are placed vertically on shaker style cabinets. They never move and so no lock nuts required.

Either way. Hold 'em up on your cabs and see which you prefer. I might go vertically. Might depend on your cab style.

Thanks guys. The knobs are going on the upper cabinets only. Here is more info.
Cabinet style

Ever hear of "fun tack"? It's a blue silly-putty-ish substance for temporarily fastening things. (Like artwork to the wall.) I've been using it to put hardware on my cabinets, sometimes for days, to see which looks best. You could try this and see which orientation speaks to you. Good luck!

Thanks fouramblues for the tip! Right now I am using my husband as the silly putty. He holds and I stand back and look! Actually, these knobs are quite heavy.

Blfenton, you are right about them not moving. They have a little tip that digs into the cabinet to hold them in place. Pretty cool!

I would say vertical--so it is like the cabinet.

Since it's just the uppers I vote vertical too, and how thoughtful of the mfr to make them so they don't twist! They look great with your pulls.

Ya know, if you don't screw them down tight (even if you do), you can just turn them. Give silly putty hubby a break! Won't they go in the same hole anyway?

Great knobs. They'll look good either way as long as they all go the same way!

My personal test is how they feel most comfortable. Close your eyes and open the cabinet with it turned each way. Choose the direction that feels most natural.

Thanks everyone! We installed them vertically and I love the look.