Stone-look surface via painting?
It's totally possible to achieve but the result vastly depends on your painting skills and your spray paint quality. 

Your can look at this page for a concrete example. 

How it compares to stone filament is fairly subjective though. Painting a 3D print usually breaks down in 3 steps : 


Smoothing out the lines. 
Achieved by either sanding the print or using acetone
Apply coating.
Ensures a better adhesion for the paint
Apply spray paint


If any of these steps are neglected, the final result won't look as good as using stone filament. However, if the quality of you stone filament is really bad, painting will offer a better result.