both great IMO, I like the F7R a lot, I'm a fan of cam-on-bucket heads generally as rocker arms dont fill me with confidence, but the F4R rockers seem reliable generally. The F7R is harder to work on IMO but mostly because of space, so it's vehicle dependent. The F7R requires a lot of special tools and procedures, but once you know them they're fantastic to work on. F4R is more reliable IMO if they're looked after