The ablative and genitive of quality (ablativus qualitatis and genetivus qualitatis) are similar. One can describe a high mountain as mons magna altitudine or mons magnae altitudinis. Is there any difference between ablative and genitive in such use? Should different cases be used in different situations, or are they completely interchangeacle?
This might be related to the difference between the ablative and genitive of price.
I think that this is largely a question of style, and the appropriateness of such expressions depends also on context. At its simplest, it might be mons altissimus: a very high mountain. A strict pedant might well stress that it is in fact the mountain that is large and, if this be judged by height, insist on magnus mons altitudine, rather than mons magnae altitudinis.
The context is important to word order in this sort of thing. It may be more suitable, for instance, to distinguish between 'a mountain that is very high', mons altissimus and 'the highest mountain', altissimus mons, discarding all consideration of a complex epithet. This is the kind of thing with which teachers years ago of Latin prose composition used to tease and torture their pupils (I speak here from bitter experience!), though it at least taught them to analyse very carefully exactly what they were trying to express.
