It depends on a lot of things. If the root cause for the failure was poor factory soldering, a new board will likely fail in the same way after similar use where as a field repair may solve the issue.

There are plenty of other root causes where many components were overstressed and replacing them all with a new board would result in less downtime than replacing components as they fail, too. Of course, sometimes you can do well with replace this group of components anytime any one of them fails.

Also, availability of full boards and availability of individual components makea a difference.