Pre-Doom Valyria vs Yi-Ti? [Spoilers Extended?]

I have been thinking about this a lot, and I would love to hear peoples' thoughts on the matter. I have not read the books (though I intend to if and when GRRM actually completes the series!), but I have spent many an hour watching various lore videos on the GoT-universe. Of the vast and captivating GoT world, I am particularly fascinated by the mysterious Yi-Ti.

Now the Mysteriousness of Yi-Ti does create problems for this question, so I think the best way to proceed is to take what we know from the account of Lomas Longstrider and supplement it with historical/mythological accounts of China. For example, it's reasonable to assume that Yi-TI probably has a standing army of a Million+ (likely in the two-three million range), and possesses impressive technology and sorcery capabilities, levelling the playing field against Valyria's dragons. Case and point, if (based on the Show) a scorpion designed by Qyburn can kill a full grown dragon, we must assume that the engineers and intellectuals of Yi-TI would have come up with this solution and then some. Indeed, is it that far of a stretch to assume Yi-Ti was more technologically advanced than Valyria? Again, relying on China as the basis for development (which was the most advanced civilization until the 1400/1500s, when they were overtaken by Europe).

Additionally, there are some things I want to throw out there for consideration:

  1. Gunpowder (probably called "Black Powder" like in Xena); Does Yi-Ti have it? Even if it is in an early stage of development. If Wild Fire is made to be such a destructive force, one can only imagine how much more destructive Yi-Ti gunpowder would be. To this end, if it exists, then it adds to the development of effective anti-dragon weapons - i.e., Imagine how much more destructive a Scorpion bolt be if powered by gunpowder. Therefore, perhaps said gunpowder is a sort of weapon of mass destruction in some regards, necessitating. In which case, it makes sense Yi Ti would keep the existence of its gunpowder a closely guarded secret; one which would only become public knowledge if Yi-Ti came under invasion, forcing its wide-scale use, and by extent its existence becoming known abroad. For that matter, given that Yi-Ti is based on China, and historically Chinese gunpowder only began to be disseminated to the West once the Mongols acquired it (over a millennia after its first literary mention), it can be suppossed that Yi Ti equally possesses gunpowder, which has not yet become known to the West.
  2. Does Yi-Ti have dragons? Chinese Mythology depicts dragons as benevolent creatures. Now, from what I understand of the lore, it is believed that dragons do exist within the far east, places like the Shadowlands (*** I may be completely wrong on this, maybe Dragons only existed in Valyria at the time this conflict would hypothetically occur***), so in theory it's possible that Yi-Ti similarly possess powerful dragons existing on the peripheral of Yi-Ti's civilization; functioning as creatures of myth, like Giants in Westeros. If Yi-Ti was attacked, however, it is possible such dragons would rise up to defend the civilization. Keep in mind, this is based off my limited understanding of the source material, and thus may be incorrect. Nevertheless, I wanted to put it out there just in case.

Now, the majesty of Valyria does not need to be expounded in this question, as the readers of this post no doubt have a much better grasp of its strength and power, then myself.

As a result, if for whatever reason the might of Pre-doom Valyria and the might of Yi-Ti clashed in a war of conquest, who would win?

I would love to hear your reasons!