Functional advantage is that ball locks have a relief valve after kegging two batches I can tell you it makes a huge difference. You need to bleed/purge the Co2 when you first hook up the gas, I needed to carb my kegs fast so I had them at 30psi for two days then I have to bleed them down to 12 psi. When I stored a partial keg I had to pressurize it to 30 then a couple weeks later bleed it to serving pressure. This week I need to transfer from one keg to another thru a jumper this involves using the pressure relief valve to make the beer flow.
With a ball lock this just involves using the valve. To do all this on a pin lock I would have to push on the poppit in the post. At the very least that's annoying and inconvenient at the worst as many will tell you beer sprays out.
IMHO its just worth it to get ball locks, unless you score pin locks for just about free then you replace the lid with a ball lock lid with a relief valve for like $15 which would be a good deal.