"On-map" or "off" ?

[Ratzki]

I have always tried to take a mortar FO if possible in my QB forces, but as of late have been taking the equivalent number of on-map mortars instead with good results. Buying individual mortar teams of same calibre as FO's does have some limitations in the way of smoke shells, LOS issues for multiple firings, and slow movements about the map, but they also have some advantages as well. The delay till the first shell drops is a fraction of the time it takes to call in an FO arty strike, accuracy with vet. teams uses less ammo, and if you do lose a team you still have some others to continue the shelling.
I was wondering what others feel on the subject, and do you feel the same about field guns vs FO's of same calibre as you do mortar teams vs same calibre FO's?