Based on our experience, I'd say you don't need either but it depends on how you intend to use your awning.
I have a 2011 Starcraft 235fb with a manual awning.
If your awning operates like mine, then the support poles actually detach from the bottom of the camper and can be placed on the ground (perpendicular to the end of the awning).
We've only done this a couple of times in 6 years and we drive a metal tent stake to anchor the end of the pole. Most time, we just leave the poles attached to the trailer and pull out the awning.
We do have awning tie-downs, but we rarely use them as we retract the awning when conditions get windy. We do have de-flappers which we install each time we put the awning out for a more extended stay.
Tie down kit:
RV Awning Stabilizer Kit - $8.99
De-flapper:
Camco Awning De-Flapper Max - $16.99