There are only three programs I have got to work with meshing for The Sims 2. Milkshape, Truespace (Only tried with version 3) and 3ds Max.
3ds Max works perfectly and natively. I suggest you do not "Convert Units" when importing a Sims2 mesh, however.
]
Truespace works great, with a plugin to export .obj files. (I have one someplace, i'll have to find it when I get home.) However, I have had problems with lighting. Slap any texture on it (in the editor) and it works. It also won't show up on the final .OBJ file.
Milkshape works perfectly, however it is totally useless for all but the simplest of meshes. Not powerful enough.
* Database dislikes Milkshape.