The potential difference would be that Italy had an existing monarchy where for example Spain had lost it and under Franco it was being groomed to succeed him. Here Mussolini still must act under the King and play to the legality of his post serving a yet higher authority. If we accept that the monarchy will acquiesce to Mussolini's de facto rule then I totally agree, unlike Franco Mussolini faces not simply his own inner party struggles but is always subject to the loss of support from the King who should command loyalty separate from Mussolini. Here the balancing act is even more precarious. So I think the question becomes how well did the Fascists actually rule in place of a democracy and how effective was Mussolini in governing. I fear the people are rather tolerant so long as peace, prosperity and success flow, the King is content so long as the people are and he suffers none for it. If you can paint Mussolini as better than average and Italy prospers then he rules to his death bed.