Here are pie charts for comparison of SF and SO stats (the two sites for which these are available). I made these for SO first, so the categories are in the order of size on SO.

Auto N means the script deleting questions after N days.

Moderator deletions and migrations are much more significant on SF. Deletion by 10K users is not very frequent on either site. Among the automatic reasons for deletion, 9-day roomba dominates on SF while 365-day roomba is most prolific on SO.

SO authors seemingly love delete their answers. Maybe because they get downvoted? Again, moderators delete much more on SF (proportionally): directly and indirectly, via deletion of parent question. The yellow Review slice is almost invisible on SF. The cyan slice, answers to migrated questions, is prominent on SF (but invisible on SO). A lot of answered questions get migrated away from SF.

Here are pie charts for comparison of SF and SO stats (the two sites for which these are available). I made these for SO first, so the categories are in the order of size on SO. The percentages are not exactly the same as in the table, because I omitted some of the obscure reasons for deletion.

Auto N means the script deleting questions after N days.

Moderator deletions and migrations are much more significant on SF. Deletion by 10K users is not very frequent on either site. Among the automatic reasons for deletion, 9-day roomba dominates on SF while 365-day roomba is most prolific on SO.

SO authors seemingly love to delete their answers. Maybe because they get downvoted? Again, moderators delete much more on SF (proportionally): directly and indirectly, via deletion of parent question. The yellow Review slice is almost invisible on SF. The cyan slice, answers to migrated questions, is prominent on SF but invisible on SO. A lot of answered questions get migrated away from SF.