It might be suggested to avoid mixing up "ID" and "Id" while crafting field:
Here is a potentally confusing usage of upper-case and lower-case "ID" token:
It could be confusing for other people while working with read-write operation on fields, content types and list items.
Besides, it might lead to unplesant typo issues.
Tend to use either "ID" or "Id" token for all cases.