They perform differently.
The 901, in my opinion, has better flavor. However, it is more prone to leaking.
The 510 has better vapor, and doesn't leak as much, but I don't feel like the flavor is as true.
Over-all, I usually go with 901's on a Kr8 batt if I'm going to direct drip. I only drip very occasionally, and at home, so I don't mind having a folded tissue to set it on when to catch any stray
juice.