I think Cardas used to use a more similar clamshell designed Furutech connector which are similar to the ones they use now with their brand name. Not sure if Cardas actually makes them in house or Furutech makes them for Cardas. I'd be surprised if there's much of a difference between the two clamshell designs sonically. They're both more affordable connectors than the more known, pricier Furutechs.
I I have used the Cardas clamshells on home brew PC's and it's a decent connector for the money. It's easy to work with and sounds good. I have WyWires PC with much better built and pricier Furutechs and that's a great cable. I'm sure the wire has much to do with the WyWire PC being so good, but I bet a lot of it is in the connectors.
Between the two different clamshells probably not much of a difference; I'm sure it was a cost decision on the change and the Cardas one is better looking of the two.
Do you have older Cardas PC's now and looking to buy new connectors to switch out? If that's the case I'd move up the Furutech line a little. Go to VH Audio to compare better connectors. They're very helpful as well.