Part of the difference is compositor integration for sure, but there's also design decisions that factor in, like how Safari has throttled JS in non-active tabs

Part of the difference is compositor integration for sure, but there's also design decisions that factor in, like how Safari has throttled JS in non-active tabs for years, where Chrome only started doing this last year. One gets the impression that Google at least is more concerned with Chrome being an attractive app platform than they are with it being responsible with user resources.