I was afraid someone would ask me that question.
I like playing with them all. The Japanese knives are new to me and I think I like them the most. I wanted a Japanese knife but it was difficult to find a good one from Japan that could be shipped to the USA. Covid closed down Japan airmail and DHL and FedEx was $100 bucks. So I decided to get the Palosanto from South Korea (6th one bottom row). It is Japanese "style", that is, it doesn't have the concave/hollow back. I don't like D2 but it is a comfortable knife with good weight. The more I couldn't get a real Japanese knife the more I wanted one. Finally Rocky Mountain leather--after being out for months--got some in stock. It is the fifth one bottom row. It is the standard 36mm wide blade and white steel. I began using that one for a project or two then I discovered Mr. Okada. He has a DHL account and it was only $20 to ship. I bought the first four, bottom row from him. The first two are 20 mm across. The third is 30 mm and the fourth 36 mm (sent to me by mistake). I think the first one is my favorite, maybe, I don't know yet. I'm right handed and I use it with the bevel on the left to cut out patterns and the like. I also use it bevel down for small skives and to trim leather handbag edges free hand in my lap after being sewn.
The two skiving knives in the middle row are Doldoki made with D2 steel. I make handbags and use them on the bag body and gusset edges. They are 2" wide and are great for long skives. I use the one bevel down for skiving and thinning swaths of leather. They both have thin handles which allow for a low attack for the skive.
The two round knives I picked up at a flea market. I reshaped them and put an edge on them. I use them primarily for belts and straps. Other than straps, I don't have much confidence using them. I will need to practice if I wanna be one of the cool cats.
I am not impressed with the L'indispensible and D2 blade. It's a good knife and all, but I seem to pick up and use a retractable blade more often. The screws stick out and are rough and I don't like the brass smell left behind on my fingers. It is designed to be held like a pencil. The blade needed a bit of stropping.
The E.A. Berg clicker knives are just plain cool. The curved ones are good for skiving large leather pieces.
The others have their uses but I don't use them that often.
If I were to only have three knives they would be #1 and 3 bottom row and the Doldoki #1 middle row.
I'm not a fan of the D2 steel. I prefer carbon steel. I maintain the D2 with aluminum oxide (white) and the carbon with chromium oxide (green) compound on a piece of MDF. I then sometimes--for fun--take it to the bare smooth side of a horse butt strop.