Still i wonder why both max users get different counts but i already heared that there are problems in different versions of Max.
There's no problems with counting.
The point is that in Max
polygon not always =
triangle. You could easily build a 8-triangled polygon, and default polygon counter will show you 1, still it will contain 8 tris, thats why I always switch on Tris counter (it can be switched under menu "Customize -> Viewport configuration -> Statistics tab")
.obj format tries to preserve "quad polys", thats why it still has polys<tris, and .3ds format always strips all polys to tris, so after import back it has equivalent counter.
Do not look at the poly counter and you will be ok! it's simple