A wire transfer is permanent. The buyer cannot get the money back. A cashier's check, even if it is legitimate, can be reversed.
I sold one of my Classic Cars for $56,000 and the buyer brought cash. We went to my bank where they assigned TWO tellers to count and verify the cash before I deposited in to my account. Since it was over the $10,000 trigger, it required being reported but because it was all verified at the bank, no red flags were raised with the IRS, DEA, or any of the other government agencies that want to stick their noses in my business.