Ready go's look like a far better way to make credits than Brackets.
May depend on how selective you are and your matchups... sometimes you get favorable matchups in a bracket.... but in open tier Ready Go's you are often competing against a group of the best players in the game where you have to play a nearly flawless round.. You might get by with one or two mistakes but beyond that... you are out of the top 10 and losing credits.
In a bracket if a top player gets a wonky round with some crazy VEM they may post a so so score for them, but nothing they would be happy with normally... You might play a flawless round and win against 1 other player having an off round... but are you going to do that against 10 - 20 elite players in a RG? You great round becomes average and you are just happy to break even or maybe squeak into the top 10.
Either way is hard, the bigger difference is ROI as you point out.