What is the difference when it comes to the final render? I understand the difference structurally and that  low res uses less memory but how does it effect the final quality?

Experiment with low poly objects and detailed texmaps
vs.
... high poly objects with low quality (size) texmaps and you'll see the difference.

The "bottom line" is to do what looks good to YOU.

The image above uses a 1 poly (one sided) square prop and renders super fast.

cheers,
dr geep
;=]

well the flip side of that is that low poly meshes are rougher with more visible edges, so you loose detail in the surface, this tends to be particularly noticable around the edges of the figure. the best texture in the world won't fix a blocky figure though it might mask some of the evidence. There are ways to smooth meshes to some extent, smoothing in Poser can get rid of some of the blockyness, Sub-D in Studio can get rid of it completely though with that you are actually subdividing the mesh at rendertime so you will still get a hit on render time.

Note - Increasing the "Crease Angle" to 100 or greater
can produce an almost perfectly round ball from the square box
which has only one polygon per side.

cheers,
dr geep
;=]

not seeing how you are disagreeing, I said smoothing can remove some of the blockyness. I dont find high smoothing angles ideal for all situations though due to some of the wierd self shading issues that happens occasionally, thats why I say some rather than all.

Ok, I agree.

Bottom line ... do what works for you, n'est pas?

cheers,
dr geep
;=]