There is a very recent thread about Card Creators that you might want to read if you are considering them. It has to do with the size of the largest of each set vs the size of the front of an A2 card. As you'll see from the thread, I have both the A and B sets and use them all the time very happily, but some people do consider this measurement "inconsistency" a problem:
Nesties Card Creator Sets A & B by Reddyisco at Splitcoaststampers
Again, I personally hadn't ever even thought about it until the OP raised the issue, and I love my A and B sets, but she (and others who agreed) did have a valid point if what she was concerned about is important to you. Spellbinders makes fabulous products, but not everything suits everybody.