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What is the major difference between hydrodynamic & rolling bearings?
Which one is used in which application?

Hydrodynamic bearings use a thin film of fluid (like oil) to separate moving surfaces, reducing friction.
Roller bearings use rolling elements (balls or rollers) to reduce friction.
Hydrodynamic bearings are often more robust against external factors.

The primary difference lies in how they handle friction. Hydrodynamic bearings rely on fluid lubrication, while roller bearings use rolling elements. The choice between them depends on factors like load, speed, operating environment, and desired lifespan.

Hydrodynamic bearings are often preferred in applications with high loads and speeds, while roller bearings are common in automotive and machinery applications.

We have a case where we are identifying the frequent failure of a finished product transportation through conveyors.
Now for such applications, what should be considerations to choose the type of bearings?

Before choosing a bearing type, classify the failure (even roughly):
Contamination wear / corrosion - bad sealing, washdown, dust ingress, chemical attack
Overheating / blueing / lubricant coking - wrong grease, overfill, too high speed, seal drag
Spalling (fatigue flaking) - under-designed load/life, misalignment, shaft fit issues
Cage failure - high speed, vibration, poor lubrication, misalignment
False brinelling / fretting - vibration + low rotation, poor fits, transport/storage vibration
Fracture - shock loads, belt slap, seized roller, installation damage
If you tell me what the bearings look like when they fail (noise? heat? seized? rust? spalling?), I can narrow the recommendation fast.

The findings which we have been able to get now are the failures related to rust happening.

For dusty application, 2SR roller bearings are the one which are recommended to be used.
They are sealed, and there is no entry of dust particles ensuring long run.
Hydrodynamic ones are not recommended due to possible dust ingress & eventual mix with the oil leading to grinding compound failing the bearing.