[glend (Glen)]

I see a fair number of threads dealing with folks pursuit of very fast f ratios. This is likely an obsession of the imagers, based on perceived time savings, but do the complexities of fast ratios justify the quest?
I have heard a fair number of experienced imagers, and visual guys, express a love for f5 as the perfect ratio. This is of course due in large part of the ease of Newtonuan collimation at f5 and slower ratios. Don't get me started on RCs, as a previous owner I have dealt with the precision required that always seemed to evade.
In the visual world, long focal lengths have historic preference, especially for double, triple star splitters, and planetary folks.
So what is your favourite ratio and why?