Deathfire Touch or Thunderlords Decree

I'm a mid Ekko and I can't decide which rune mastery to get; I decide to look up what other people said and the responses were mixed.

"Thunderlord's is better early game and/or before you pick up some AP, Deathfire is better late game unless you're still behind in items. Specific champion synergy matters." According to a thread, that was the Tl;dr. ^

So I'm thinking Thunderlord's Decree so I can possibly snowball a bit more early game? Does that sound about right for a mid Ekko? :P I build mostly up to 200-300 AP and get one tank item.