I have both, but find it hard to compare them, even though they are virtually the same size in terms of length.
Carry: The Sebenza is thinner and lighter. The PXL is a heavy knife. You notice it. It doesn't carry as well in the pocket.
Blade: I like the Sebenza here. It has a hollow grind and is much thinner. The spine of the blade is also rounded for better comfort. The PXL is a heavy blade with a thick spine and low saber grind. It does have a nice false edge.
Steel: How do you compare a 3G laminated blade to a solid S30V steel. I'd guess the PXL would be a lot stronger, both because of the lamination and the thickness of the blade. The 3G core is quite a bit harder than the Sebenza, so it should hold an edge longer. My Sebenze gets small microchips that detract from the cutting performance. The 3G responds faster to stropping, which is something I like. I think the PXL wins on steel, but I haven't fully tested it. I know Nozh doesn't like it, and he has impressive tests to back up his opinion.
Operation: The PXL wins easy. It is so smooth it's almost silly. The thumbstuds are longer and easy to catch. I can snap the blade out with a flick of the thumb and no assist from my wrist. Can't do that with the Sebanza. The PXL is plain fun to handle, and it oozes quality.
Quality/fit/finish: The Sebenza probably wins, but a lot of the Sebenza's features are so subtle that most people won't notice. When handling the PXL, you notice more sharp edges from the thick steel liners and spine of the knife. Nothing sharp on the Sebenza but the edge. But the quality is more noticeable on the PXL.
Lock: I'm not one to worry about the type of lock, as long as it's solid. The Sebenza is a frame lock, and the frame is titanium. The PXL is a liner lock, which most people don't like. But this liner is more like a frame lock because the steel liners are so thick. Both are solid locks that are not going to fail in hard use. If either of these locks fail, it's because you have much bigger problems.
Looks: Well, the PXL is beautiful, especially with white micarta scales. The Sebenza is an acquired taste. If you don't know much about knives, the Sebenza is not going to look attractive. The PXL will look attractive whether you know anything about knives or not.
Both are great knives.