Quick answer
Both are flame-retardant house wires. FR-PVC resists the spread of flame on standard PVC insulation — reliable and economical. FR-LSH adds low smoke and low halogen, so in a fire it emits far less smoke and toxic gas.
If fire safety and clearer escape routes matter (homes with children/elderly, crowded buildings), FR-LSH is the better pick; FR-PVC suits budget-sensitive general wiring. See the full FR / FR-LS / HR-FR-LSH ladder.
Compare APAR Shakti FR-LSH and Shakti FR-PVC.