Quote from Moneyball:
Again, your examples are obviously going to work out in your favor, since that's your argument. Where are you picking these figures from? No one that I know that scales out does so in 2 increments, one at 50% of target and one at 100% of target. Maybe they take some off at 75%, some at 100%, then let some run to 125% and 150% (just as a slightly more reasonable example). Assuming equal lots at each level, tell me, who makes more money, this scaler or someone who unloads it all at 100% of target?
Besides, in your first example, you're assuming that every trade that the scaler got out at 4.5 pt profit would've reached 9 pt. profit before getting stopped out. Do you honestly think that's practical? If one trade doesn't do that (which is very likely in reality), the results of the two "systems" change drastically.
See, any one can come up with hypotheticals to support either case. In the real world, things work a little differently. The only situation in which going all in/out will always outperform scaling is if you know the exact bottoms and tops, which no one does.