Jetpack Protect and Limit Login Attempts

Although the end result is the same, both plugins work differently: Jetpack Protect not only checks for failed attempts on your site, but also checks for that IP on all other sites running Jetpack and all WordPress.com sites. An IP can consequently be banned before it can even make one attempt on your site, if it was banned somewhere else before.

You could continue to use both, though, that won’t hurt your site.