the hair / fur default workflow generates geometry in mantra rather than use the sop during rendering.
this method has many disdvantages.
1: if your guide groom nodes display is off…the hair generate will not render
2: it is very buggy,i have had many scenarios where relatively light hair (less than a thousand strands)took hours to render,i also have had scenarios where the hair is visible in the viewport yet will not appear in the final render

all these problems i easily solved by choosing the “use SOP geometry ” button on the hair generate node…
my question is why is this not the default,
seeing as it is more stable and faster?

why would anyone prefer the mantra fur procedural method?…what advantages does it have or what scenarios would using it be preferential…thhanks

There's a few reasons, that I'll try to outline. The mostly have to do with resource usage efficiency.

1. Skipping the step where curves are generated at ifd creation time prevents having to save out potentially gigantic per-frame geometry files, saving diskspace and network bandwidth.
2. Deferring curve generation to the render step allows expensive hbatch licenses to be released sooner, so that free mantra licenses can be used for the majority of the process.
3. ifd generation can be allocated to machines with fewer cores, less ram, and/or run more jobs in parallel, thereby increasing hbatch license usage efficiency. Since the mantra step is going to be done on the largest possible machine anyways, curve generation can be performed more quickly with the heavier resources that are usually dedicated to raytracing.

If you do not split ifd generation out into a separate step and do not have a render farm, then it probably makes no difference whether sop geometry is rendered directly or not.

oh thanks..i knew they had to be a good reason.