Difference between thick vs thin front suspension? I visited a bicycle shop a few days ago. I noticed two different types of bikes. One with thick front suspension and the other with thin front suspension. Bike with the thick suspension was more expensive.
Does thick suspension provide benefits or just add weight?
Is thin suspension more better than thick one?

Thick Suspension:

  

Thin Suspension:

            

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Fork-leg diameter is not really how you would classify suspension forks. Or more exactly, it is a way, but not really the most relevant.

Suspension forks could be classified by how much travel they provide (different travel for different specific uses), the suspension mechanism (springs, fluid, elastomers, air, hybrid), the damping mechanism, etc.

I suspect that both those bikes were pretty cheap, both probably use spring suspension, and neither is really intended for hard off-road use. A bigger-diameter tube isn't necessarily heavier, as it can be made with thinner walls.