According to the Ares site, it seems there are 4 sets of ship stats thus far. In order of Maneuverability, Burden, and Maneuver Deck, we have Frigates at 7/3/A and 8/2/C and SoL's at 5/5/B and 5/5/D.

To recap - Maneuverability is the range allowed between each maneuver card you select (bigger number = better)
Burden is the amount of damage you can take before a box closes out (bigger number = better)
Maneuver Deck is the deck of cards you get to use for movement (unknown, but assume A and C are more agile)

There are an equal number of each (2) in the Wave 1 release ship packs. In the KS exclusives there are one of each. I can't tell on the starter pack ships, but for equality I would guess there are one of each (swapping Nations). That would make a total of 4 of each stat set.

Of course, there maybe other things on the ship log that differentiate them, or not. I don't know. I just found this out when I was looking at what to expect (as CPT) and if I might want to sell off a few of the ship pack ships as superfluous since it seems a person would want to run a single ship (two at upper most) and I doubt I will have more than 5 or 6 playing the game ever. Of course, the variety allows me to run a table of SoLs or Frigates or unequal mixes so I likely won't be parting with any of them