F10 is stock HUD view on targets showing speed and distance to only your locked on target.
F9 is no HUD at all.. basically, you can't see speed, shields, etc..
F11 is full HUD, which is distance and speed of all targetable items, plus asteroids (even non targetable ones)
I usually use F11 HUD especially in asteroid fields and in PVP when it is more than 1 vs 1
The game should automatically reset to F10 view after each mission finishes.. if it is not, then something in the game is messed up or you may have altered some setting in the SFC.ini file by mistake.. however there is not a known setting in the SF.ini file to make F11 the default view..
However if you are using Key bindings for a certain ship, I think F11 can be set to a default key binding on each specific ship you set.. but that would only be in effect if you have F11 HUD enabled before and after you set the key bindings..
Hope this helps.