Home Forums Hardware Mac Desktops & Notebooks When to replace imacs and Macbooks?

There's no "general" answer to your question.

I'd say that the most compelling reasons to upgrade are that your Mac can't run the latest operating system (Both of yours can.) or you need more computing power, that the most compelling reason to stick with what you've got is money, and that there's an awful lot of room for likes, dislike, and idiosyncrasies between the two.