The difference is probably just how long you let your play session go for. Since there are so many things to do on p2p, you likely spent more time in game... thus got more events. F2p has much fewer things to do, so you'd get bored and log off. On p2p, I remember getting tons of events while doing that rune sudokan minigame... each puzzle took like 10-20 min without me realizing it, and after just about every one a random event would pop up... but you won't see me standing around for 10-20 min consistently on a free world.