AppleInsider purports that the part numbers themselves — 101, 103, 105 and 107 — represent the storage capacities of the Mini, ranging from 8GB to 16GB, that “A” and “B” represents the Black and White color options, and that Good/Better/Best represents WiFi, 3G and 4G LTE connectivity respectively.
Because there isn’t just Good/Better/Best. There’s also Good BTR, Better BTR and Best BTR. 101 and 103 both receive the BTR part numbers, while 105 and 107 do not.
I’d argue that Good/Better/Best refers to storage capacities, probably starting at 8GB.
The A and B, I agree, are the Black and White colour options.
So what are the numbers?
101 and 103 have also have a “BTR” designation, which suggests they’re in some way unique from 105 and 107.
I’d speculate that 105 and 107 are WiFi and WiFi+Cellular models. And that 101 and 103 are, in fact CDMA variants for the Cellular model for Verizon and Sprint.
P107 Good B would, then, be a WiFi only, 8GB iPad Mini in White.
P103 Better BTR A would be a CDMA (Verizon, maybe), 16GB iPad Mini in Black.
And so on.
Another theory could be that 101 and 103 “BTR” are actually Wi-Fi and WiFi+Cellular models with Retina Display, BTR being an abbreviation of “Better”.