I must admit i prefer P2P aswell, atleast the way EVE does it. No sign up cost, no cost on expansions just 15 bucks a month for everything and then the optional PLEX ingame if you are rich enough. Also server maintanance and upgrades have costs too.
Tho i must admit when i calculate what ive spent on WoW over the decade ive played i can see the argument against P2P. But all in all i did have fun in WoW except the last few exspansions which i tried but never got into really.
The B2P can work for some but you would need an ingame store to purchase goodies and whatnot. As many have pointed out and i agree with is that this takes precious development time away from the core game and spends it on fluff or swag or what ever its called today.