If a person has tough skin with smooth, round contours and uses good technique, then almost any of the sharper blades can work, regardless of beard type. Though if one's beard isn't particularly thick or the hairs not too wiry, an extremely sharp blade may be overkill.
Experienced DE shavers have usually stumbled upon a few blade brands that work for them. It is often newer DE shavers that are flummoxed by the multiplicity of options as well as contradictory and misleading reviews of blades on the Internet.
The first step that a newbie should take is to get the right razor or close to it. To help in that regard, I strongly recommend a careful review of my two-part article, "Picking the Right Razor for You."
Once you have a razor that is in the ballpark for you in terms of shaving capability and gentleness (degree of potential harshness), then you can start to narrow your blade options, but it will eventually come down to trial and error. However, by intelligently analyzing your skin and hair, you can save yourself time and money by eliminating unlikely options right from the jump.
If you find your skin to be sensitive (as mine is), a combination of factors will contribute to potential skin irritation:
- How frequently you shave; that is, daily or less frequently?
- The shave characteristics of the razor itself (again, consult "Picking the Right Razor for You")
- Pressure of razor against skin (very light pressure is best; more pressure leads to razor burn, nicks, weepers, etc.)
- Is your blade sharp enough to easily cut your whiskers? (If not, you may have to press too hard or make too many strokes.)
- Is your blade too sharp? (For those with sensitive skin, too sharp might be irritating, particularly in the wrong razor or with less-than-ideal shaving technique.)
- Type of coating, if any, on the blade (coatings can make the blade less irritating)
- Skin protection offered by your shave prep
- The average number of passes (strokes, really) that you make during your shaves
That said, once you have a razor that is fairly suitable (again, be sure to consult my picking-a-razor articles), resolve to make your initial shaves reasonably close, but not baby smooth. This will allow you to shave in one or two passes, thus helping to minimize skin irritation while you perfect your shaving process and gear.
Also, if you're in doubt about good shave-prep protection for sensitive skin, I've become fond of shave sticks, and in particular, Arko brand. Onto a wet beard, one can rub the shave stick directly on the most sensitive areas such as upper lip, lower lip and chin, below the jawline, or any area with lingering irritation from a previous shave. Then with a damp brush, this layer of soap can be face lathered and spread over the entire beard. The soap itself with sufficient water is slick and protecting, and the initial application of the waxy soap on sensitive areas may offer a bit of extra protection.
Now as to blades, for all shavers, one should get a blade sharp enough to handle one's beard. If you have sensitive skin, however, the idea is to get a blade just sharp enough. It should also have a coating for additional smoothness. The exact coating and the durability will be up to you to choose and determine. Implementing these suggestions can prevent unwise or silly blade choices.
For example, let's say you shave every other day, have sensitive skin, and for a first razor bought an Edwin Jagger razor, which has sufficient blade gap to comfortably shave a two-day growth (and also often comes with a potentially-slippery smooth handle, but that's another issue). But your beard hair is rather fine and thin. To buy an ultra-sharp blade such as a Feather would be asking for unnecessary risk of weepers, nicks, and general skin irritation. Better to go with a less-sharp blade with a good coating for smoothness.
Another example: You have sensitive skin but still prefer to shave daily. You wisely bought a Merkur 33C, a Lord LP1822L (L6), or equivalent because those razors are great daily shavers even on sensitive skin. However, you have a thick, wiry beard. You heard good things about Derby Extra blades and are about to try them. But this may not be an optimal choice. The chosen razor head is a face-friendly razor, but your beard is tough, so you need to pair your razor with a sharp, coated blade that will both be able to slice through your tough beard hairs without simultaneously irritating your face. Look for sharp, but smooth blades. Several options might be better such as perhaps Polsilver Iridium Coated, Personna Blue, Astra Superior Platinum, SuperMax Titanium, and other coated blades that are near the sharper end of the sharpness spectrum.