With centrifugal impellers, the key factors are the OD, the vane angle, and the depth of the vanes at the outer edge. Just based on the photos, I’d say all three factors are the same for these two impellers. Differences at the ID end of the vanes makes little difference.
I broke my impeller trying to get it off, so I went to a junkyard and looked over the selection of Chevy water pumps. I selected one from a big block Olds or some such that fit but looked completely different, the vanes were only slightly backward-leaning while the Jag vanes are strongly backward-leaning. They looked kinda like the one in this pic:
Presuming that Chevy knew more about keeping engines cool than Jaguar, I installed it and it worked well. However, looking online at the assortment of Chevy water pump parts available today, it seems apparent that most of them look very similar to the Jag part! Simple fact is, they may be the Jag part, meaning Jaguar may be simply using a Chevy part rather than making its own. Here’s a pic of a typical impeller:
It’s also worth noting that many Chevys and other cars use impellers that are stamped out of sheet metal rather than cast iron. The sheet metal is usually stainless steel, so while they may look cheap they are most certainly more corrosion resistant than the cast items.