I was casting for the first time in months last weekend. I was using Lee molds I got for Christmas. One mold is a two holer that makes 440 gr WFNGC for the 500 Smith & Wesson. It started dropping nice bullets after 4 or 5 cycles. It got hot enough to start dropping frosted bullets, so I rotated to the 6 hole Lee 300 gr WFNGC .452 for my 454 Casull.
This mold is a beating to use. Getting good bullets to drop from it was a chore and took a long time. That's when it occurred to me that getting consistent heat in a long, multi-cavity mold is the challenge. Still, I admit that when it started dropping good bullets it dropped 6 at a time, so that helps make up for lost time getting it running smooth. But I can't deny that the 2 cavity mold is just easier to get good bullets from.
In fact, it was no problem rotating back to the .501 mold and getting good bullets out of it after it had cooled back down some. Meanwhile when I rotated back to the 6 cavity .452, it took a few cycles to get it running again.
The value of the 2 cavity mold is that they are just easier to use. At least that's my experience.