I was about to say Gallia of the Endless Dance since she seems broadly more applicable to a wider range of decks with more interensting synergies than stormbind, but I have a better hot take: you shouldn't play either of these cards right now.I have the most difficult decision to make. I decided to go down on gold cards, which is more or less easy for me in 9/10 cases, but it also means I have to cut one card from my gruul section, one of two who work with gruul madness (as I don't think having both gold card be signposts for the same deck would do my cube's variance any justice). But which one?
I like Gallia since she lets me discard cards for free on turn three, that's Wild Mongrel-rate and enables agressive starts, which is cool. But Madness doesn't always have to be super aggressive, Stormbind has been very good in aggro too and I think it has more application outside of that specific deck.
Please help, I feel unable to make a decission here.
Since you're shrinking your gold section, now would likely be a good time to test some new cards that fit with your archetypes instead of trying to choose a favorite among cards you've already played. Specifically, this guy:
This card is really popular because it scales, but I like it even more here than normal. Unlike Gallie and Stormbind, Kavu gives you the ability to discard the card you want to cast for madness, making it an extremely effective madness enabler. It can also be applicable to temur and jund madness builds since it grows with the number of basic land types you have in play. In addition, it provides a little bit of graveyard hate, which can be relevant against flashback spells and the like. It even comes in the cool retro frame!
Basically, Territorial Kavu has the positive aggressive atributes of Gallia without the Satyr flavor text, the discarding prowess of Stormbind without the random clause, and several unique glue elements in it's own right. This card is a great synergy piece and now is the perfect time to give it a try since you're already downsizing your gold section and need to cut a different madness enabler. Cut both and give this a try for now!