Sedation and ga differ depending on the combination of drugs used. Ga provides a full lack of consciousness allowing vets to perform anything painful (I.e surgery, dentals). Sedation does not lead to a full lack of consciousness and animals are usually aware of sounds going on around them and depending in the depth of sedation they may be able to react and even move whilst sedated. Sedation is suitable for procedures that may be uncomfortable (but not painful, such as positioning for X-rays) or scary (such as clipping matts of fur/poo) when we need the patient to remain still. Sedation is achieved with injection and can usually be reversed with another injection, leading to a quick recovery. GA is also achieved with an injection only, or with an initial injection followed by intubation and inhalation gases. In cases when ga or sedation can be used the vet may prefer to give a ga and intubate the rabbit as this can be safer than a sedation because a clear airway is established with the intubation tube, meaning that the animal can be 'breathed for' by the nurse if they stop breathing by themselves. Old or debilitated rabbits are often safer being anaesthetised and intubated if the vet is able to. Sedation is not deep enough to allow for intubation.
Hope that helps
(Registered veterinary nurse)