DESPISTADO it is obvious, that these renders has the different params (I can see that in the second (faster) image, where antialias is turned off) maybe the other params was simplified to
Next issue is render time - without light set and Iradiance or GI I newer get rendertimes more than 40s, even if the scene is too complicated
Now about the main theme - "MESH vs. POLY".
The poly ones is the same mesh, but has a lot more of editing tools, and is mainly created for moddeling in quads (four sided planes) when mesh mainly operates on triangles
There is no big difference in renderring, but alot of lag in viewports (Mesh review is much faster than the poly ones), thats why discreet created a new tool called TurboSmooth, it smooths the poly or whatever you want to smooth, and shows the result as simple mesh, because it decreases the lag in the viewport (but has no effect in render time).
So, I think that we dont need to discuss about that, infact, I'd suggest you to disscuss about "POLY vs PATCH", it'd be more usefull than this :P
Dont be angry at me, and sorry for my bad english