I have always wondered why there are two ways to convert geometry. Can’t everything be wrapped up in one?
Don’t use editable mesh, ever. Just Editable poly, only thing that works without major problems.
Editable mesh is older, i think they kept it in because of downward compatibility.
Max is full of old features which no one uses anymore because they got replaced with new features.
Good if you whant to open a 10 jears old scene but bad for new users. I´ve seen many totaly confused students ^^.
I show normal’s a lot and the editable mesh is the only way, unless I am missing something. You always hear to collapse the editable mesh and other things referring to it.
Let’s say that ‘Mesh’ is universal, and ‘poly’ is 3dsMax way of interpreting the meshes
When working with imported cad data (Catia, solidWorks, step, Iges..) lots of time mesh is the income and gives a lighter, more predictable and better result. So there is still a huge use for mesh, and yes it is usefull.
But when starting from scratch, directly in 3dsMax, Poly is the way to go.
I need Poly because I build my houses with Poly Modeling. So, I guess there are purposes for both, but why not combine them?
And for your use, you could always use the ‘Edit normals’ modifier, that allows you to show the normals on editable poly if you want
I import a lot of arch viz CAD geometry which comes as a editable mesh. I typically leave it because when I collapse it to edit poly some meshes just break a do wired stuff.
Improvement of the editable poly tools would be nice, to include all the legacy features, I agree.
However, this is a great thing to keep everything in there, MeshSmooth is still in there, and for some very specific cases, works better that turbosmooth. (And turbosmooth still exist, even if we have OSD, and so on..)
What you probably need to do is go to edge mode, ctrl+a and check visible right at the bottom - in edit mesh it’s possible to hide edges to get a cleaner look, but if you convert to edit poly it cant see those edges and tries to re-mesh it only using what is visible… makes for interesting results sometimes.
Cad import hides edges automatically if there is less than x degrees between them on a curved surface.
That was it! thanks Neilg! now I just have to find a script to do on hundreds of objects at a time. 
Fundamentally they are different data types under the hood. The way the data is stored works differently between the two so it’s not a matter of ‘just combine’. There are some good old writeups from Bobo on the CGtalk forum that explains why things are different between the two. Here’s one
Ah ha nice!
I have cad data all the time.
If I convert them to poly, it just f*** up the whole mesh, so I’m obliged to keep it in edit mesh, but I’ll try your trick on the next one and see how it goes!
Thanks
Stan
The hidden edges thing catches a lot of people out. Once you understand that Editable Polys are basically always trying to re-jig their geometry (which is why functions like dividing/connecting edges are so much smoother than Editable Mesh) it makes a lot more sense.
I remember reporting a bug when Autodesk introduced the ‘isoline display’ in the Turbosmooth modifier during beta testing. If you collapse any object with Isoline display enabled to an Editable Poly it doesn’t restore the hidden edges (as it does when you use Meshsmooth) and it basically ruins the mesh. Got told it wasn’t a bug. It still does it now. Hooray!
As SnipeyX mentioned, mesh and poly is totally different thing under the hood.
Mesh is more friendlier for computer.
Poly is more friendlier for user.
Best workflow would be working with poly and publish with mesh.
Mesh use a lot less memory.
We have an asset which is 350M if it is poly.
When I converted to mesh, I got 250M.