Difference between these? D350, D329, M101-4/5

[SethY]

I am very confused as to the differences between the sets I listed above. Aren't D350 Standard Biscuit and D329 Weil Baking the same as M101-4/5? What are the differences that have them graded with different titles?

I am specifically interested because of some of the cards I see on eBay. All the D350 and D329 cards seem exactly the same as the M101-4 and M101-5 cards I see as well. Also, while searching through the board archives, I see people ranking rare backs of M101-4 and M101-5 and including Weil Baking and Standard Biscuit...but aren't they different because of how they are titled (D350, D329?)

Are any of them rarer and more valuable than the other?

Someone please help me by shedding light on my questions! I would greatly appreciate it as I am looking to make some purchases of certain cards. I would like to be fully educated first, though.

Thanks!

Seth