They are "probably" all made in the same factory, but each will vary slightly with composition of lead/alloy content, slight differences in weight/head size/pattern etc. which will depend on the Di it is cast from and the makers specification requested. As a Di wears this in turn changes the pellets size/shape etc, so they are all actually in a constant state of flux to a degree.
The only way to really know is to try some and see, but remember the batch number is as important as the Manufacturer and "model" you select, you could find a good tin of AAFD for example and the next tin you buy is not so good as it's from a different batch, so a lot of people try a few tins, select the best, then buy in bulk of that batch number form the base of the tin.
As an example - I've attached a test I done with half a dozen batches of the same pellet - JSB Exacts 4.52, but all of different batch numbers - it's very enlightening to see the difference there is batch to batch - or as people experience - tin to tin?
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This also explains a lot about manufacturers returning guns under powered, the difference between one batch and the next can be a full FPE, so it depends where in the power curve it's tested and also if they are using an "efficient" batch and you are not - or vice versa?
James