why tilting pad thrust bearings are preferred in heavy and high speed machines?

Answer 1

A hydrodynamic wedge of lubricating oil is formed by the rotating collar causing the stationary (non rotating) pads to tilt. Because the load is distributed across an oil film any slight mechanical variances which would otherwise cause unequal load distribution are equalized across the oil wedge. The load is equally distributed across all tilt plates as each plate generated its own wedge of oil.
If you used a contact roller bearing instead, each ball would have to be the exact same size to exactly distribute loading. This is not realistically achieved in manufacture or maintained in operation. Under heavy loads one missized ball would cause a large shift in force distribution resulting in excessive wear ect...

So for heavy loading requirements the tilt plate justifies the added expense over a roller/ball thrustbearing

Kingsbury thrust bearings are commonly used on ships to transmit the force from the propeller shaft to the hull.

Answer 2

Capacity for enormous loads. Much smaller. It can adapt to changes in load and speed giving better stability. Very low maintenance requirements so great for submarines.
A supplier
http://www.sartorius.com/index.php?id=844
The wiki entry
http://en.wikipedia.org/wiki/Air_bearing