hmmm, man I chose wilderness just because of the fun-factor, but staking is definitly a money-farm. Tbh when pking not every walking loot that strolls by is risking over a mil, but its common for people to stake 1mil plus and with no food either, a 1-2 minute fight with a definite winner, no running, and someone getting a mil or more!
Although I had to go with wilde, its more team oriented which is great to chill with your m8's, you occasionally come across a nice loot like smiting a big item or catching someone risking an oddly high amount of gp which is nice, and its just more exhilarating to me.