What is the difference between an editable poly and an editable mesh?

The edit poly mode bring modelling features that editable mesh haven't (fast tools to work on edgeloops (rings and loops selection, connect tool, etc), and other goodies like "extrude along path" that can save time, it's like the Meshtool script but integrated in max, and in poly the soft think in polygons (n-sided) and not in tris (in poly mode, the polygon counter count the POLYGON and not the tris).
i hope i've answered to your question

Dear Mr Reem, Thanks for commenting on me as an expert, but I'am not, any way what I thought was very simple when comparing the answers you have got already.
According to me there is no big different than it saves the rendering time, and depending on your work, the editable poly mode has more features than the '' MESH" mode.

Read this...
I hope it will help http://www.max-realms.com/modules/newbb/viewtopic.php?topic_id=1682

In general there is no difference between an editable poly and an editable mesh that goes beyond the practical tool set as described by being either a poly object or a mesh object.
Regardless of which you use every object created in 3d space is minimized to three points in space required to define area and shape.
In Poly editing a quad-poly is nothing more than two tris with the divided edge hidden.
It might look square but it’s still built from triangles but the tools available to the edit poly modifier, things like loop and ring for example, requires quads to function properly.
The use of the Editable Mesh is still useful though as it does have some features available that are not available to the Editable poly.
The majority of all 3D applications support the editable mesh allowing for importing and exporting.
An Editable Mesh “will” weld vertices regardless of the condition of the object.
For example a Editable Poly will not weld co-sided edges, think two plane objects with a third intersecting to create a “T” shape, which could case problems if you plan to use a simulation, create facial targets using an inner mouth, or mess up smoothing groups.
But The number one reason why features and tools are not removed, even when they seem redundant, is 3ds Max is an applied application and once a feature is included in the box it can not be removed with out risking breaking a legacy file.
As to which you should use use what works.
It’s easy enough to convert from one object type to another and it’s not a case of what works best but what works best in a given situation.
http://www.digitaltutors.com/forum/showthread.php?26387-Editable-mesh-Editable-Poly