If player makes progress ~1 skill point per 2 green tokens it is better to use power training. If he progresses slow use PT. Also players who want fast advance, use PT. Power training takes TIME. PT is almost instant. TIME is biggest tradeoff.

Fast advance in less time requires PT.

Advance in 1-3 days require, days. Both require tokens, so tokens are out of equation.

Also if you get more expensive player, it is good chance that he will make 1 SP per 1,5 green token with power T. So only question is can you wait several days.

Next but also important calculation is injury. Every training is chance for player to injury and be off pitch for days. PT does not have that option. Injury requires tokens +50 if u train more than 2 players at same time. PT does not require that much RED tokens. That is also important for calculation. Heavy training makes more injuries, more red tokens, total training is more expensive.