Which technology is cost effective when compared between SLS and SLA

Comparatively SLS will be low cost because of the price of  build material and post processing techniques.

In which technology better surface finish is achieved SLS or SLA

In SLA technology we will achieve better surface finish because of  build material properties, output will be like moulded plastic part

In order to achieve toughness, which technology is preferred either SLS or SLA

SLS will be preferred because the build materials are typically nylon and hence tougher than average SLA resins

In which technology we can get clear prototype

SLS has no chance to get clear output , whereas in SLA some resins are translucent and some are clear. To get clarity, you will need to polish the build part

Which technology is used for fabrication of hollow parts in 3d printing

SLS is used for manufacturing of hollow parts as there is no support generation required whereas in SLA support generation is a mandatory step, which will be tough to remove supports during post processing, in case of hollow parts