It's quite clear to me that a stag Patronus is more physically imposing than an otter would be. Is this still the case for its ability to ward off Dementors, and general strength?
I realise the shape is determined by personality, etc, but it seems (to me at least) that Hermione's otter might indicate she has less of a store of positive emotions, at least compared to Harry, to draw from. Likewise for other wizards whose Patronus takes a non-imposing animal form.
Is there a breakdown of animal forms taken by Patronuses and their user's relative aptitude at using them to ward off Dementors?