If this player is your primary trainee and the others aren’t as high priority, no- one position training will always trump two-position training in terms of effectiveness per player. However, if you have 5-6 guys you’re prioritizing about the same amount, two-position training will allow all six to train, just slower.
Training pressure for just PG will result in an OD pop on average every 2-3 weeks, whereas PG/SG would give you a pop every 3-4 weeks, though I’ve seen it closer to the slow end. This is assuming an advanced level trainer (leave 4) and no secondary trainer to focus on your youths.