If the aerial in use receives the normal current analogue signal for terrestrial stations -that's the one to use,
It rather depends on your local conditions/transmitter etc.
Anyway start with what you have and play from there.
For example I am 20 miles or so from Crystal Palace transmitter.
My old[30 yr] loft aerial works fine for the main TV.
My Freecom Digi USB thingy for the Computer works from the supplied stub aerial suckered on the the north facing window in the 'puter room- which makes it in the completely the wrong place- but it works fine.