The first ball that MoRich released that had a large pin was the Onslaught. Every ball they introduced since then has also had a large pin.

The concept behind the large pin idea was to allow the bowler a better visualization as to when the ball began revving and started its transition from skid to hook. By watching this transition, one can determine how soon or late the pin begins to migrate to the axis, how sudden or lazy this transition happens, and wether or not it continues pulling towards the axis or starts to go away. When practicing, many knowledgeable bowlers will place a large piece of tape on the pin to see all of this and get a better understanding of why their ball is reacting the way it is. However, during competition the tape must be removed (according to our governing body, now the USBC). So basically, what MoRich did was they designed a 3/4" (roughly) pin to resemble the piece of tape that can be used in competition. A GREAT IDEA and TOOL!! (although there are some bowlers that deem it to be ugly or a distraction )  

When Columbia was manufacturing there equipment (the Onslaught and Mayhem), the pin was designed to be about 3/4", but if it cracked or chipped during manufacturing, it had to be drilled out and re-pinned (or plugged) and the size increased. That is why some of the pins are larger than others.

Now that Brunswick is manufacturing there equipment, they can't do a 3/4" pin. The largest they can do is roughly 5/8" (which is still about 1/4" larger than the standard 3/8" pin). I don't think Brunswick runs into the problem (or at least a lot less than Columbia) of there pins cracking during manufacturing as I haven't seen any with real large pins.

The Ravage and Total Annihilation (both manufactured by Brunswick) had just the 5/8" pin. MoRich wanted to go larger on the pin for the WMB since it really helps to show the continuation that this ball is capable of. But, since it couldn't be done, they opted to start using a circular shaped "Pin Logo" for the ball. This was also another GREAT IDEA because now it takes on the appearance of being almost like a bulls eye target that seeks the axis and it took the emphasizes of the larger pin. Hopefully this tactic will be received better by those who say they were distracted and also cause newer users to take notice of how the "label" pulls to the axis, allowing them to become more educated with making them feel they have to "learn" something new.....God Forbid  

Hope this helped!
KIK