Didn't do too well selling on Ebay, though. The "High bidder" never got in touch, didn't reply to direct messages & was eventually reported to Ebay. They also didn't get any joy from the muppet, so I was then able to cancel the sale. Didn't pay the final commission fee due to the situation, but still got stiffed for the listing fees. The bike did sell privately, though for less than the non-paying Ebay bidder had supposedly contracted to pay.
Last private sale I concluded (the Classic 500) was paid for by a cash deposit + bank transfer. No issues with that purchase either. All new car, bike & motorhome purchase in recent years have been by either bank transfer prior to collection or Direct Debit at the point of collection - all problem free.
I guess you won't learn much from the trouble free transactions of whatever means - it is the troublesome ones & how easily (or not) that they were resolved that would be of interest. I had an "interesting" situation with a cash purchase when I sold my Caponord many years ago. It was a commission sale through the dealer who I bought it from (easier at the time due to work commitments). He took cash for the bike & handed it over to me minus a couple of hunderd commission. But the buyer was a milkman who took in a lot of cash & for whatever reason a large chunk of the £4500 was in Scottish £50 notes. The (English) bank were deceidedly windy about accepting that ! The cashier had never seen a Scottish £50 note before & got her supervisior involved, who had every note checked with UV before finally accepting it.