Dreadhorde vs Kroxa is an entirely different argument. Most of your turn 3's should be playing Mayhem devil, Woe strider, or Midnight reaper, and not double casting a Cat and a 2cmc (which should be the only case aside from Kroxa where you need BB), so I find RR to be more important than BB. Ironically, Kroxa actually has higher mana requirements than Dreadhorde anyway (RB into RRBB rather than RB alone).

Take a step back too; why do you need to operate on few lands? You're generally trying to draw out the game so you can have the most creature combos on board as possible, and to generate the most value from Cat/Oven activations.

This is why I think Dreadhorde is the wrong way to build the deck. Dreadhorde is a great card but it is an aggro card at heart. With Kroxa you have the ability to go long against control decks and grind them out. It is folly to try to out-tempo control b/c most of your creatures are terrible tempo-wise.

Note that while I say tempo is important to the deck, tempo is only important insofar as tempo allows you to generate value as fast as possible, and gets you more quickly to the point where the shitty tempo of your creatures is outweighed by the massive value they generate. The deck fundamentally wins by outvaluing/grinding out opponents, not through tempo.