If I was to hand till either rabbit manure, or alfalfa meal into the top 4" of a raised bed, which would be the best soil amendment?
What does the soil need? Rabbit manure analyzes out to about 2-1-0.06 while Alfalfa meal analyzes out to about 2-.05-2. Both are sources of slow release Nitrogen, but the rabbit manure is better in soils with adequate levels of vegetative waste mixed in as well so the Soil Food Web has something more the chew on.
It is not so much an either or question as it is what does the soil need.
If you were planting immediately, and the rabbit manure hasn't been composted, I'd go with the alfalfa meal. Much less likely to burn plants in my experience.
Rabbit manure is considered a "cold" manure because the Nitrogen is not all that readily available as it is in Horse and Poultry manure and is unlikely to "burn" plants. However, because of the potential for disease pathogens in manures the recommendations for using manures in the vegetable garden are to apply them 90 days from harvest for above ground crops and 120 days from harvest for in ground crops.
My rabbit manure has always burned any plant it has been applied to because it is always mixed with plenty of pee. I suppose it would be fine if the rabbit owner was able to get the bunnies to pee and poop in separate places, but most of the time that's impossible.