NickB

I would agree on the cheaper, on the whole (although depending on when you travel, Thello from Milan to nice can be as cheap as €15.00, which is about what you would pay for the cheaper flixbus fares between Milan and Nice). I would, however, disagree on the "faster" and "more comfy". On "faster", thereoretically, the quicker bus services take about the same as the train (4 3/4 hrs to 5 hrs). However, they are far more prone to delays than trains for a variety of reasons, including random police/immigration checks in France. Departure location in Milan is also an issue. Most buses leave from Lampugnano bus station, which is hardly a central location, compared to Milano Centrale for Thello trains. As to comfy, you get substantially more space in trains than in buses and you can stretch your legs far more easily than in a bus. While I have not done MIlan-Nice as such on a bus, I have done Genoa-Nice (and beyond) a few times. it is OK, it is cheap and I have absolutely no qualms doing it again but, all other things being equal, I much prefer the train to the coach in terms of comfort and reliability.