easy answer will be polygon handle
1. poly by poly - every polygon u draw and manage individually: pro - low detail objects, cons - hell time expensive
2. subd modelling - adding a layer of subdivision to have a better smooth over the mesh: pro - faster, cons - lots of on/off switches between hpoly and low poly mesh
3. cad softwares manage easily fillets and round shapes: pro - u have to worry only about shape, exports will handle polygons -> perfect for concepting, cons - can't manipulate so easy as poly-modeling softwares
& integration
game: cad - retopology
film & render: most dosn't care