At 100+ ping, p2p would become unplayable competitively, whereas client/server could potentially be competitive at 150, possibly even 200. (But nobody wants 200.)
hehe.. we used to manage pings 150-225 all the time back on dial up. You just have to lead your shots. 300 was unmanagable then.
Today's kids are soo spoiled. ;D We used to DREAM of sub-100 pings. That's why we would have lans. These days, you still have to connect to an outside server and then back if you want to "LAN" with current games. Local networking has been done away with.
In some cases, you can set up a private local server, but it's a lot more difficult than it used to be. AND it can mess up your stats if that's something you care about.