That is very useful information! Regarding hippocampal lateralization, I think an asymmetry may not be known broadly enough in the imaging community (after checking, I now see it in a recent dataset, at approx. 2.5%). This may particularly be an issue to consider when researchers are using atlas-based ROIs, as sometimes they want (and assume) equal numbers of voxels in left/right ROIs.
(Also, I should have qualified my answer by noting that these aspects of the AAL may be concerns if you are considering an fMRI study of a population.)
However, I would quibble about the AAL hippocampus definition, as it does seem, to me at least, to be more *precisely* defined than the rest of the atlas, with respect to excluding white matter. (e.g., compared to frontal regions - unless the atlas brain has a huge amount of grey matter!) If this is the case - and it may not be - there is probably a good reason for it, but nevertheless it may be something to think about when using such this ROI.