The first number like "5000UE" is the model number of the cable. The second two numbers are for Westlake's stock. The 500 or 1000 refers to the size of the roll. These numbers have no bearing on the cable. That said, if you're looking for a higher strand count cable, the 5xxxUP cables tend to have a higher strand count. This is not apparent on Westlake's website and you need to check out the product link at Belden's site.
If you were thinking of 12ga cable, the more flexible one is the 5000UP which can be found
here. It has a 65-strand count, as opposed to the 19-strand count of the cheaper 5000UE.
Her's a product link for the
5000UP. I personally have the 5000UE cable (the less flexible one) and while it's fine for my purposes, I can honestly say that I wouldn't want to be pulling it through a wall.