Using OBJ as source for GPU related APIs has at least these well-known issues:
1.) support for polygons with more than 3 vertices,
2.) usage of independent indices for positions, normals, tex-coords,
3.) is text based.
All of the above issues cause an essential amount of work to be done during import. Moreover, OBJ is AFAIK meaningful useable for static meshes only. With this in mind, OBJ is not a well suited format for use in game engines. It has limitations even in its use as input to tool chains. So, even if the mesh is exported with triangles only, not all problems are solved. OBJ seems to be a relatively simple format, and it actually is during the process of parsing, but it turns into headache if one wants to use the resulting mesh with modern graphics APIs.
Edited by haegarr, 16 July 2014 - 06:12 AM.