First, some definitions. I guess "safety razor" can refer to any shaver that makes it difficult to cut yourself, but I'm specifically talking about the older type, like this:
Claimed advantages of safety razors:
- Recyclable blades
- Less irritation
- Closer shave
Ok here's the reality:
Most people will compare by saying these blades are like $0.50, compared to $5.00 for a branded razor cartridge. True. It's still true after you factor in the upfront cost - good (and you need good, because a lot more depends on the razor here) razors, a stand, and a brush might cost $100, depending on how much you want to spend. But the difference narrows when you consider the ongoing costs - soaps and aftershave. The thing is, these razors need a good lather to work. Nobody shaves dry with these. And good soaps are expensive. So you have to stick with it for longer than you think to break even.
IN THEORY, the blades are recyclable, since they're all metal. In practice, look at what people have to do with their old blades. I'm not saying they just don't recycle them. They even need to take special precautions to dispose them. Because these blades aren't "safety" out of the razor. Rusty, used razor blades are hazardous. So people put them in old cans, containers, stuff them into holes in the wall (seriously). Also, almost all household plastics are recyclable, but how much actually gets recycled? Are there recycling facilities for razor blades in your country? The bottom line is, you're not going to recycle these blades, and you need to think carefully about what you're going to do with them if you have children in your house.
Less irritation/closer shave
I think this depends a lot on individuals, skin texture, hair coarseness, etc. I'll just point out this is a claimed advantage of cartridge razors as well. Again, in theory, with the huge variety of razors and blades out there, you should be able to find one that works better than a cartridge razor for you. Ok you can get a sampler blade pack with maybe 10 brands of blades. But how much are you going to spend to find the right razor? And are you going to try each razor with each blade?
I haven't seen anybody say safety razors are faster than cartridge. And they're slow. There's more preparation to be done. You have to go slow. What you save in money, you may be losing in time.