Upload & Sell: On
My initial reaction is that #1 is by far the most distinctive. I look at things from the perspective of a trademark lawyer, so I have a particular bias. Among trademarks, distinctiveness is power.
The chief purpose of a trademark is to identify to consumers who the source of the goods or services is. Second to that, a trademark might -- might -- be able to convey information about brand identity or value proposition to the client on first glance, but this is a lot less common than most people think.
Numbers 2, 3, and 4 all mimic hand-signed initials, which, I'm afraid, is very common among photographers' logos. This undermines each of those options, because it makes them harder to distinguish from other photographers' logos, and thus harder for a new prospective client to remember.
By contrast, the first one has power precisely because it is unexpected. If it makes a viewer think "car," then the viewer is somewhat surprised to see that it in fact indicates "photographer."
This worries some people, but it's less problematic than you might think. Consider, for example, how often someone unfamiliar with your work might see your logo completely out of context. It's conceivable that no one will ever see your logo apart from your images or some other material that identifies you as a photographer, and even if someone does, in that instance, there's a high chance the viewer is irrelevant to you.
My question about #1 is a design question. Why did the designer separate the arm of the "k" and make it a gradient? Was that just aesthetic, or does it have some significance to your style or identity? (Just being an aesthetic choice doesn't make it wrong, but I always wonder whether elements like that are purposeful or merely fanciful.)
I'm glad to see the designer in #1 appears to intend to provide a solid along with the gradient. Gradients do not reproduce well at very small sizes or as watermarks, so you'll probably want the solid (i.e., all-white or all-black) version to use for those purposes.
I dislike #3 because it is annoying as a watermark. As a knockout (i.e., empty space for the letter knocked out of the color or white or translucent square), it occupies and obstructs too much of the image. By contrast, the bold strokes of the letters in #1 will work very well as a watermark, even if you use them without your full name underneath.
So I strongly favor #1.
There's one more thing to consider. I infer from the variety of colors that you did not indicate a color palette preference. Red is exciting, blue is cool, so you might be biased in favor of #3 just because of the respective designers' color choices. But if you aren't starting off with a specific color requirement, and if the designer of #1 can produce it with red (or orange or yellow) rather than blue, it might be interesting to see how it feels. I don't know whether that would be an improvement or not. But the industrial feel of #1 might be mitigated slightly by a different color choice.