multimode fiber vs single mode

Is there any reason except cost to use multimode against single mode fiber.

where multimode fiber can perform better than single mode ?

Nope if costs were the same you would want to use single mode (it goes further)

If you're considering which kind of fibre to specify make sure you think about the kit that will be going on the ends of it and your current and future speed requirements. You can mix and match on the ends but the fibre you've installed will limit your choices. As Nevins says, single mode is the more future-proof choice

in multimode multiple light paths are available will this feature benifit over single mode ?

Not in terms of the speed you can get, multimode and single mode provide the same. Single mode however can support longer distances