A mate offhandedly said "trample is the best ability on a threat" the other day, as if that was obvious. He meant of the more reasonable combat abilities rather than things like hexproof and indestructible. Even so, intuitively I value flying more, and this is reasonable when you consider lower cost cards. Trample is a scaling ability and at its best on bigger dorks, being of little to no value as the creature's power tends to zero. Most magic is played at smaller mana costs and so on average flying is worth quite a bit more than trample. As are things like first strike and menace. He was right though. There is a point at which trample is going to be getting more done towards closing out a game than flying is. This is obviously going to have to be a discussion about averages as there will be every context under sun where trample on the smaller dork is better than flying on the bigger etc. That all in mind however, trample can't be chumped, it has to be met with toughness. You can't so easily shut off combat damage triggers and things like lifelink on a dork with trample. Give a trample guy deathtouch and it is about as scary as it gets. So, simple question, on average, at what power value trample better than flying?
It is a bit of a loaded question really as ever is the case in magic. Even if we are averaging across all games and all matchups it is still both format dependant and affected by the toughness. For simplicity we will just consider X/X dorks where toughness equals power. This is somewhat the norm. For a rough rebalance when considering lopsided dorks, I would tend towards flying as toughness gets lower than power. On a 4/3 flying might be worth more than trample, while on a 4/5 it might be the other way round for example. There is also the general consideration that flying has defensive capacities and trample does not. This means in slower decks there is absolutely added utility in those fliers. My mate did however stipulate "threat", which means you are hoping to close the game out with it rather than stall. Threat also implies big, which is how his statement could be so simple and yet so casually accurate.
(Amazed this Sphinx is the closest I could find to a vanilla 5/5 flier for 6!)
So, with all those caveats out the way, when is trample better than flying on a threat? I can only speak to the various cubes I have played but it is around the five power mark. On average slightly above I would say, like 5.5 or something meaningless like that. I think however it is the case that a few outliers, specifically against green where you are preferring a flyer to a trampler quite some way up the power curve. As such, I think if you disregard green and then consider again then my estimate of 5.5 drops to somewhere below 5 power at which trample is on average better on your threat. Anyone else with any differing ideas on when the crossover happens, or anything further to add on the matter I would be interested to hear. Beyond that, this is a mercifully short article. I have slapped down an opinion on what I think the number is for that cross over point, which is five or a bit over that if we are allowed fractions, but I can't really justify it or demonstrate it, it is simply a feeling based on experience.