In Rails, update_attribute method bypasses model validations, while update_attributes and update_attributes! will fail (return false or raise an exception, respectively) if a record you are trying to save is not valid.
This means that if at certain point during the project you adjust validations such that some records that used to be valid are now invalid, expect your code to stop working without any obvious reasons. This will happen because update_attributes will no longer update old records properly, but unless you check its return value, you’ll never know that it’s failing.
I stumbled upon this problem at least twice in the last month, and decided to write it up to finally remember to do it right next time.