The Cardigan is larger. They weigh more and are a little longer.
The Cardigan has a tail.
The Cardigan has rounded ears compared to the Pembrokes more pointed ones.
Pembrokes come in black tri, red, and sable.
Where the Cardigan comes in those colors, but also black bi, and blue merle.
From my experince and from what I have read the Cardigan is also a little more layed back then the Pembroke. The Pembroke can be a little intense sometimes.
Another diffrence is availablity. Pembrokes are a lot easier to find then the Cardigans at least on the West coast.
I would love to own another Cardigan. Next one though I would like a puppy. That will be down the road some though. Since my husband said the only Corgi that is going to live in our house is Magic. My current Pembroke.
Cardigans are difficult to find in the midwest as well. We searched for over a year. Our daughter then went with the Pembroke. They are a delightful dog. I prefer larger dogs, but little Ellie has stolen my heart as well.