Sorry, but I don't have the answers you're looking for. Then again, if I did you really shouldn't just take my word for it. If you are unsatisfied with your current chalk, I encourage you to try every different chalk you can get your hands on. There's bound to be something out there you'll like.
To answer your question in my own smart-alecky way:
What's the difference? Well, it's like the difference between Coke and Pepsi. They look the same, they do they same job, you'll never find out *exactly* what ingredients they each have inside, and some people swear by Coke while others love Pepsi.
The interesting question is this: If a new brand of cola came on the market, was priced over 100 times more expensive than the leading competitor, did the SAME EXACT THING that the other colas do but for some odd reason purported to be better, and garnered large numbers of zombie-like followers that belittled Coke and Pepsi drinkers, would you switch?
I've been using brand "M" chalk my entire life for 2 reasons:
(1) 99% of the time, it's the only chalk I ever see on a pool table. And I've been all over this country playing pool: Bars, pool halls, state and national tournaments, amateur and pro events. Everywhere I go, there's brand "M" chalk for *free* just sitting on the rail of every pool table.
(2) I've never even thought of buying a different brand of chalk because brand "M" does it's job perfectly. Far too many players refuse to believe that miscues are the fault of their bad stroke. It can't possibly be their fault. It must be the fault of their tip or chalk. If only someone would make a fancy non-miscuing tip, or invent a magical cube of chalk. Then they could forgo the years of practice required to develop a good stroke, and they'd finally become the champion of the world!
(No, I'm not ripping on you because you asked about chalk. Again, try all the different chalks you can. I'm ripping on the die-hard chalk aficionados.)