I think the three other SKUs are for Airport products, bringing you the 802.11ac standard which will be included in the new MacBooks:
"Good" for Airport Extreme
"Better" for Time Capsule with 2TB
"Best" for Time Capsule with 4TB
Would perfectly make sense, because Apple has to support 802.11ac when including this with new MacBooks. Otherwise you would not be able to use it.
Can I have two timecapsule in my network? Can I backup one computer to one and another to the other?