National Socialism was really a bit of both, when compared to the Fascism of Mussolini’s Italy, being both more conservative, and more revolutionary at different times and on different subjects.

If we consider traditional conservatives in the early 20th century, they are broadly constitute what we may call the ‘old right’. The ‘old right’ represented the old elitist structures and bases of power which had existed prior to the democratisation of the 19th century, that is broadly speaking - the interests of monarchy, the landed classes, and the church.

In contrast, Nazism represents a form of what we may call the ‘new right’. Rather than hoping to gin back the clock, as the ‘old’, National Socialism has gained power in Germany through the organs of mass politics - the political party, rallies, and elections. Mussolini’s fascism may also be considered a part of this ‘new right’.

However, what separated the two - Mussolini’s and Hitler’s forms of fascism - was their respective reliance upon the traditional structures of power. Mussolini allowed both church and king to remain in Italy, and with a considerable degree of power. Hitler meanwhile did not, and there was to be no authority outside that of the newly established Nazi state. In such a fashion, Nazism was to some extent less ‘conservative’ than Italian fascism.

However, the revolutionary character of the Third Reich is somewhat hard to determine. It’s overarching goals were certainly revolutionary of course, but much of its policy implantation in the early period was quite limited. The regime was keenly aware of its insecurity in 1933, and so policy was slowly implemented, remaining inside the realm of public consensus and what would essentially not bring the regime under too much criticism. With time, and growing support, Nazi policy would become increasingly radical, especially during the war. So it’s somewhat difficult to describe the revolutionary character of the party due to its inconsistent nature. From its conception to 1933 though, we can see a fair amount of revolutionary character - the use of street fighting and paramilitaries, attempted coups (Munich Putsch), etc.

In terms of racial and imperial policy, the Nazi regime is clearly also more radical and revolutionary than the Italians. The 1935 Nuremberg laws were both more stringent than those produced in 1938 in Italy, and followed to a greater extent. Certainly Italian racial exclusionism and colonialism was deadly and brutal, but it paled in comparison to that of the Third Reich, which worked towards a total reconstruction of central and eastern Europe’s racial demographic. Nazi policy resulted in the campaigns of mass murder executed in the ‘final solution’, alongside mass deportations, the extensive use of slave labour, and the wilful starvation of millions of Soviet (and other) POWs.

So really, this type of comparative question is hard to answer, it will depend upon what you are judging specifically. Nazism was very much predicated on a racial basis that is not so evident in Italian fascism, or at least not to the same degree. As such, racially the Third Reich was more radical, as it was with its rejection of traditional bases of authoritarian power.

If I was to pick, I would say that Nazism likely entailed a more revolutionary change to society and the world. While Mussolini wished to recapture the glory of the old Roman Empire, Hitler and his henchmen desired to create something new and utterly terrifying, calling for a level of brutality in the process that is almost unimaginable.