Why invading Malta would be worse than Crete

If the resources used to conquer Crete were diverted to Malta, would the assault go badly wrong?

Yes. Malta's difficult landing terrain and established defensive arrangements made the prospect much worse than simply transferring the force used at Crete.

Malta's terrain offered few safe landing places for parachutists. Urban areas might provide flatter surfaces, but landing there would put isolated troops among a hostile population. The island also had established defensive infrastructure and continuity in its defensive arrangements. Crete provides the comparison: a late change of commander and staff could leave a replacement trying to reconstruct the existing plan with little preparation time. Judgements differ over how much blame belonged to the replacement commander personally, while agreeing that the disruption harmed the defence.