There's a lottery for the $farm tokens every hour. You don't get tokens every hour. You get them in the hours where your mining power wins the round.
It's a mix. if you buy one you can concentrate on raising that power, but others might gang up on you to slow you down. If you're diversified you are less effected by any negative impacts, but it's also harder to drastically move the mining speed up of your tokens since they are distributed.
Diversity is less risky, but where there's risk there is potential for reward.