I don’t advise you to buy as much as possible, if you are considering cassettes from bic - then choose orange ones, they shave perfectly, and it feels like they don’t get dull at all, enough for 7 times a close shave.
These, blue, blunt already out of the box, you can use them to collect spools from clothes.
Has pros:
My experience with bic blades is based on orange cassettes, I thought there was no difference, but it turns out there is.
Cassettes have no advantages, they shave the same way as dSee full review