Has the TV got HDMI connections? You say it is not HD. It may of course be "HD ready". If both machines have HDMI capability then yes, an HD cable is better than scart.
Well hdmi cables are a lot easier to manage (no pins and a lot lighter).
Also they are digital and scart is analog so in a while scart will be obsolete anyway (many new TVs don’t have scart sockets)
I think that you may find that you may need to use HDMI 2 for your recorder and dedicate HDMI 2 when you want to use the recorder, unless your main TV (sky box, didital box, whatever)is routed through the recorder . If so use HDMI 1. Of course the firestick may be what you are using in which case that will be in HDMI 1, and again the recorder goes in HDMI 2. The choice of HDMI 1or2 is on your TV remote in the AV input menu.