Originally Posted by 13901

As a local, I disagree.
The bus from Turin is a better option as it's direct and, crucially, avoids Milan.The route runs along the A4 motorway, which though usually busy is also very fast-flowing, and then leaves for the SS336 state road at Marcallo-Masero, which is before Milan. In fact, the A4 grows from 3 to 4 lanes in both directions after Marcallo.

If the OP were going to, say, BGY or LIN, where he'd need to go through Milan's ring roads, then I'd have suggested the train.

I've taken the bus a few times when I was living in Turin. Personally, it's never been a big problem. And I'd go to MXP perhaps 2hrs before, definitely not 3. Security can be slow, but these days the longest/most annoying wait in MXP is passport control for those flights going outside of the Schengen area. For some reason the airport authorities got e-Gates there, and they got some SITA product that takes ages to scan a passport (assuming travellers know how to use them, which seems very hard). Considering that non EU passengers still need to be stamped out by a human, it's incredibly futile.