I've seen a few credible side by sides done by growers such as
@ttystikk if I'm not mistaken. They got lower yield on defoliated plant. I've also followed good growers who believe heavy targeted defoliation works. When I compere those grows to other good growers who don't defoliate the results are in favor of those who leave the plants alone for the most part. Topping and training is not quite the same, especially if you are on a perpetual with no mother, topping slows them down yet increases yield in the long run on top of (more importantly) keeping that cutting going. With no space for a mother that would only leave seeds as an alternative option for many. You want to get into seed sogs?, that's the obvious efficiency trade off. Veg light electric costs less than seeds.
Defoliation is very subjective and the lines are blurred. People who do too much defoliation don't speak about the added flower time it introduces, they also don't talk about how vegging too long forces defoliation in order to not over crowed > bud rot, rather than actually reducing plant count removing the need to defoliate. Heavy defoliation also increases veg time and is a huge loss in both perpetual and singular, be it time or annual weight. If you only have 2 weeks to veg, use more but smaller pots. If you have more time, use less but bigger pots + topping. It's a balance, if you need to defoliate you're getting that balance wrong. We all have or will make this mistake, obviously not all will see it that way and change.
It does not pay to be an emotional person who gets attached or worse still blinded by ego. Do what ever works and change on a dime if something does not. You can find enough evidence on riu alone to see that heavy defoliation is counter productive. A picture says 1000 words and it's true, 95% of growers who advocate heavy defoliation at any point here on riu have shitty low yielding, fried and tired looking plants, go see those.
The whole point of wisdom and history is to learn from the mistakes of others. If you can do that it is truly a gift and one hell of a game changer.