@MatCauthon3, @JonOli12 and others who base their arguments for Unit viability on Pop efficiency,
I think you have something to learn about optimal play.
Pop efficiency is far too overrated by the herd on online forums, I suspect this happens because lower level players tend to wait out their games and are far more likely to reach 200 pop all the time, compared to how the game should be played optimally(like in 1650+). Not only that they also play unusual closed maps or high res/post imp-esque settings.
If you are a frequent watcher of pro games since many years, or a pro yourself, after seeing how the game is played optimally, you know that it is only the Cost Efficiency(ROI- return on investment) of the unit-line that matters everytime, it and it alone dictates the unit choices and counters, and also decides the game.
And this Cost Efficiency is majorly affected by not only unit cost but also unit speed(MAJOR FACTOR), counterability of unit(WORST for EA and WE) and net damage output per unit(number of hits) and millitary building cost.
That Population efficiency does not directly figure in any significant way into Return on Investment(ROI) calculations, should be fairly obvious.
Easy to understand if you have an understanding of economic indices.