In my testing with mardu midrange, I have found dragon fodder to be the better card.

The three drop slot in the deck is super clogged, and this allows for an easier curve with more consistent play in the early game.

Because the spell is in the two drop slot, it offers an interesting option that I have chosen to experiment with. Crazy though it may sound, I am not running seeker of the way. As I have constructed the deck, the focus is heavily placed on token generation and feeding butcher of the horde. Running fodder in seeker's slot frees outburst's slot to hold two mardu charms and two kolaghan's command. this vastly improves the U/B control matchup, as well as giving the deck much needed answers to early threats in the game, as it facilitates early game thoughtseizes, chained to the rocks, lightning strikes, and dragon fodders.

This being said, I do not believe fodder is strictly better than outburst, in fact, I would say that the two are different enough to require separate evaluation in any given deck. I believe mardu midrange wants fodder because the three drop slot is so clogged in the deck that it needs it's token spell to occupy a lower slot, where the deck typically didn't have much game.

I also must attest to how powerful guaranteeing a turn three stoke is over attempting to set up a turn four stoke. Outburst may enable a three land turn four stoke, but hordeling outburst can always push through a turn three, two land stoke. That is a powerful play, and it can mean the difference between surviving the early turns of the game and floundering turns 3-5 whilst you dig for answers off the top of the deck.

Simply put, mardu needed early turn plays that enabled it's late game spells, and fodder more effectively feeds both Butcher and Stoke the flames, while dragging your curve down and even going so far as to enable a turn four, six power rabblemaster. Anything that speeds up the clock Rabblemaster provides is sure value. Outburst fights Rabblemaster for tempo, whereas fodder just adds momentum to the strategy.

I am not saying outburst is a bad card, but hot damn does fodder do some heavy lifting in this deck...