Opinion? Vanguard engines are possibly the best "new technology" engines Briggs & Stratton ever marketed.
But to make your query "equal", you need to come up with a specific "engine family" in the Kohler brand line-up.
On this forum, I think the Kohler Command engines receive higher marks than the Kohler Courage engines.

What is the intended application? Vanguard engines are designed for heavy use, if you want to mow an acre of lawn once a week they are over kill. OTOH, if you intend to run the engine long hours under load, the series is worthy of serious consideration.

Vanguards R good, by far an away the best thing out there
in the Briggs line-up... Kohler Commands aren't bad either..
Paul R...

Are you repowering or is this a new purchase? You can do no wrong with the Vanguard, it's Japanese, or was. The Command is still in production and finds its way into several commercial applications.