I use PayPal because it's easy and relatively thoughtless, like me. I figure in the cost when I buy or sell.
Plus, they got me $200 back when a scammer sold me a bike he didn't own or have.

eBay has become more or less a place to shop with a huge selection. Figure in shipping and what you want to pay, and take it or leave it.

It's also a good substitute for on-line gambling and gaming. Sometimes you win, and get stuff, and sometimes, you lose, costing you either nothing or you get the booby prize when the piece of junk arrives.

At least the "house" doesn't get all your money, and you get something in return, every time.

I still see some bargains, in fact, I know of a couple right now. Maybe it's a matter of wanting something no one else does.

Selling, however, is getting more complicated, on eBay and CL.
First, it costs more on eBay than ever.
Second, the questions, on both.
Third, the non-payments on eBay, and false starts on CL.

Overall, though, I'm finding parts I'd not have been able to even think about getting before. The market is world-wide. Some of my bikes would not be my bikes if I didn't know I could find parts on line. Period. There weren't exactly a ton of classifieds listing the bikes I own.

I'd have exactly one two bikes, if all I had was the classifieds: 1989 Pinarello Montello and a 1965 Schwinn Heavy Duti. And someone would have beat me to them, as it's likely that interested buyers were looking on CL and eBay, instead. I might still own them, too, but eBay and CL made it possible to ship them for the investment plus about 3 bikes in profit. Hmmm...5 bikes vs. 2. I'll hang with the hassles for a while more.