Should I nip out the tops of Petunias?

I just let petunias grow , they seem to branch and bush up OK by themselves. When they are growing I do cut back the odd stem that seems to grow at twice the rate of the others , this is just to keep it in shape . When they are growing they do benefit from regular deadheading.

 

I buy Surfinias from my local Nursery (I've no heat in the Greenhouse and it's chilly up North until May). When I buy them they've already been nipped, which seems to make them a broader plant and a strong plant.
Petunias I seldom actually buy. I prefer Begonias for pots.

 

I let them grow too, they branch and bush-up well enough by themselves (and as with anything pinching out the tops will put them back a couple of weeks I reckon).

I'm doing Red, White and Blue this year, to be patriotic ... but only the Red and Blue plugs have arrived so far (that was ages ago, they are about to flower now ...) so gawd knows what it will look like :(

 

Snap ! I am doing red white and blue as well Good job I bought them , as all my salvias have caught the dreaded lurgy and I have lost them all