The specs are pretty much the same between earlier and later sub-generations of Apple keyboards, but there are internal differences in the switches. AEKs had serial numbers up to about 1M, but AEK2s do not have serial numbers and there were probably a lot more than a million of them made.
Personally, I have felt more difference due to age, wear, dirt, etc, than the generation of switch. For example, in a vacuum, I prefer orange to pink/salmon, but clean fresh pink would surely be preferable to beat-up orange.