This is one of the oldest arguments in grooming, and most of the advice out there is written for guys who never had a bump in their life. For coarse, curly hair, the number of blades on your razor actually changes what happens to your neck. Let me break down how each one works so you can pick with your eyes open.
How a multi-blade cartridge works
A cartridge with three, four, or five blades is built for one thing: an extremely close shave in as few passes as possible. The first blade pulls the hair up and out of the follicle a hair's width, and the blade right behind it slices while the hair is still lifted. That is called hysteresis, and it is why a fresh cartridge feels so smooth. The problem for you is that it cuts the hair below the surface of the skin.
A hair cut below the surface has to grow back up before it clears the skin, and with a tight curl, it often turns back in before it ever gets there. That is the exact setup for a bump. On a neck that already swirls and flares, a cartridge can quietly work against you every single shave.
How a single blade works
A single blade, whether it is a safety razor or a straight razor in a barber's hand, does not lift and slice. It cuts the hair right where it sits, at the surface. You give up that last bit of baby-smoothness, but you keep the hair tip up at skin level where it can grow straight out instead of curling back in. For bump-prone skin, that trade is almost always worth it.
There is a second benefit. A single blade makes one clean cut per pass, so there is less dragging across the skin. Less drag means less of the tugging that irritates a sensitive neck. It takes a little practice to get the angle right, but once you do, most men see their neck calm down within a few weeks of switching.
When a cartridge is actually fine
Do not throw your cartridge in the trash. The skin on your cheeks and along your cheekbones is calmer, the hair usually runs in one clear direction, and it bumps far less than the neck. Plenty of men run a cartridge up top where it is easy and switch to a single blade or a trimmer on the neck where the trouble lives. There is no rule that says one tool has to do your whole face.
Whichever you pick, keep it sharp
A dull blade is worse than the wrong number of blades. Whether you run one or five, the second it starts to tug instead of glide, it is planting bumps. Swap safety-razor blades every few shaves and replace cartridges before they feel rough. A sharp blade of any kind, used with the grain and a light hand, beats a dull one every time.
My honest take from the chair
If your neck is your problem area, start with a single blade there and a good with-the-grain technique. Give it a month. Most men who make that switch come back and tell me their collar stopped feeling like sandpaper. If your skin is easygoing and a cartridge has never bothered you, there is no reason to change what works. Match the tool to the skin, not to the marketing on the package.
EvenHue reads what the camera can see and coaches your grooming. It is not a medical service, does not diagnose or treat any condition, and is not a substitute for a dermatologist. Anything that looks like more than grooming, see a professional.