soft will give most grip and little life
med a tradeoff between life and grip
hard will give less grip more life ...
and the amount of life and grip depends on the tire it self ...
and its the tire it self thet will determine if a paticular tire will give good grip or bad grip on what surface ....
inserts is just amount of grip vs life ....
but then again this will depend as the surface is not always the same .... even tho its the same vanue ... with changing track temp and ... humidity ... also not forgetting nitros fuel if there are nitros running and ALSO not forgetting the the track surface willl be after rubber beein laid down by other cars
so it depends and its too hard to say what is good where and when ... too many dynamics ...
so to keep it simple ....
get the GOOD tire everyone is using there on the track and then select between a trade off of life vs grip