High horse power and belt drive over direct drive,
and more importantly a good quality blade.
But a lot of blades now are more material specific, go to the Montolit website and view their blades, they have some very high end and excellent cutting blades. But they’re generally material and job specific.
Personally, if I have around 2 dozen blades, and they’re all very different in different situations.
They may work on one brand very well, but even when it’s exactly the same tile, if the batch is different, suddenly it won’t give a clean cut.
It’s a minefield, and as everyone has said above, it’s our holy grail, all you can do is find the one that works best on that tile, that day!