I think it depends on the childminder as to which is better!
Some are really good at socialising the children they have - so I think that would be just as good nursery, but if they don't then I think thats a bit poop for the child!
At nursery you want to feel comfy with the people who will care for her, and that you like the sleeping arrangements, food they offer etc
Ofsted do reports - these a good indication of how good they are, but I personally think gut instinct is the best way to see things!