I haven't tried every blade out there. Everyone has their own idea of which blade they think is sharpest and YMMV. Out of the ones that I have tried I would say:

1. Astra SS
2.Astra SP
3.Voskhod

Although the Voskhods are pretty sharp they are just not comfortable for me at all. I've tried them off and on and each time I find myself replacing it with an Astra. I really want to try Feathers tho to see what all the hype is about.

So far for me I'd have to say the following:
1) Feather Black
2) Gillette Silver Blue
3) Shark Super Chrome
However Gillette 7 o'clock Green is moving up and may well replace one of the above after my current Focus shave. Voskhods haven't even been broken out yet so the above list may be exploded by the second week in January!

I haven't tried every blade out there. Everyone has their own idea of which blade they think is sharpest and YMMV. Out of the ones that I have tried I would say:

1. Astra SS
2.Astra SP
3.Voskhod

Although the Voskhods are pretty sharp they are just not comfortable for me at all. I've tried them off and on and each time I find myself replacing it with an Astra. I really want to try Feathers tho to see what all the hype is about.

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I used Feather Black in my Focus shave and was impressed. My next Focus will be for my NEW SC to see which blade I'll be using in it. Already decided on Shark Super Chrome's for my DE89bl. Once I get my NEW sorted out I'll have my razor rotation set.

I would definitely put feather and Kai blades at the top and let several others Duke it out for 3rd place

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Kai blades look crazy expensive. $37 for 100. To justify that much on blades with so many other low cost options they would have to be really good. They may be though. But at that price Feathers are a whole $10 per 100 cheaper.

Kai blades look crazy expensive. $37 for 100. To justify that much on blades with so many other low cost options they would have to be really good. They may be though. But at that price Feathers are a whole $10 per 100 cheaper.

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KAI lasts about 5 times more shaves than Feather for me. I falsely claimed they are thicker than other brands in another thread. They are not, but they are definitely more stiff (more hardened), and keep edge better than most brands I have tried.

I definitely want to try more blades. I'm always searching for the ultimate close/comfortable shave. Ones I've tried that I absolutely don't like. Crystals, Gillette 7'oclock (Green), Shark SS, and Sharps. Maybe I'll trade a 100 Astra SP for a bunch of different blades with someone on here. I have 390 Astra SP and 200 SS. But I like the Astra SS better so I'll just keep those and trade out the SPs

Kai blades look crazy expensive. $37 for 100. To justify that much on blades with so many other low cost options they would have to be really good. They may be though. But at that price Feathers are a whole $10 per 100 cheaper.

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Kai and feather are certainly more expensive than most other blades. I actually don't get them often because of that fact. I like voskhods and Gillette 7 'o clocks the best overall, but the OP didn't ask what I liked. I'm assuming he wants to seek out the sharpest blades possible to try out.

Of course, if you are seeking longevity, that crown jewel would belong to the personna 74.

The best way to go about figuring this out would be to get a sample pack from tryablade.com
Amazon and eBay also offer a lot of samples pack options.

I think as @swarden43 notes above the problem is the notion of a blade being "sharp". As far as I am concerned all razor blades are sharp....and I have the scars to prove it . Now smoothness...that is a different matter. They all cut stubble...some more smoothly than others. I have tried many blades and not all blades are smooth. I can identify two blades that I think are smooth (and sharp): GSB and Astra SP. I am sure there are others.

Problem - an ojective sharpness test has yet to be done (that I am aware of).
Thus, there is no answer to your question, merely opinion.
Sorry.

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When it comes to blades, I think sharpness is the only thing that can be tested without shaving. So far my simple naive yarn test has shown the same result as when doing a real shaving test. By shaving I would sort the tested blades like 1. Feather, 2. Rapira PL, 3. KAI, which is exactly what the yarn test also told.

Of course sharpness is not the only factor when one is picking a blade. One can not by non-shaving tests say what will be the best blade for somebody. There are so many different ways to make a blade and different coatings. Even though Feather is sharpest, it is not necessary the best blade for me.

When it comes to blades, I think sharpness is the only thing that can be tested without shaving. So far my simple naive yarn test has shown the same result as when doing a real shaving test. By shaving I would sort the tested blades like 1. Feather, 2. Rapira PL, 3. KAI, which is exactly what the yarn test also told.

Of course sharpness is not the only factor when one is picking a blade. One can not by non-shaving tests say what will be the best blade for somebody. There are so many different ways to make a blade and different coatings. Even though Feather is sharpest, it is not necessary the best blade for me.