I live on a farm and catch rainwater.  So (pesticides, solvents, pharmaceuticals, chlorine, flouride) aren't much concern to me.  I'm more concerned with (grit, leaf litter debris, algae, bacteria).  To that end I have two filters.  The outer filter is 20nm pleated.  The inner filter is 1nm dense mesh.

When I had my water tank cleaned and they refilled with chlorinated water, I swapped the inner filter for a 1nm carbon filter.  But it's been swapped back now.

If I were to do it again, I don't think I would change it. 

 The carbon filter makes a massive difference in my opinion. I can’t stand chlorinated water, so we got a plumbed fridge with a carbon filter and it honestly takes 95% as good as rain water