'the aussies' kept the ski jump because that was cheaper. the canberra class's design is so that the ski jump takes next to none actual deck space, as it is on the very edge of the bow. the fact that they didn't use the spot right next to it for parking, like the invincible class does, says enough about the need and/or possibilities for deck park on that spot.
the drawback of an ramp is that it takes space for helicopter. the advantage of it is that it shortens the runway you need for STOVL aircraft, which frees space for helicopters and parking.
keep in mind that the invincibles originally were envisioned as helicarriers first, harrier carriers second by the RN.
I really begin to question what makes you the amphib expert here, gator country