I'm trying to give the most measured assessment of Ponga and Newcastle that I can here.
My general assessment is that Ponga could be equally good in the 1 or 6.
He has the defence, kicking, running, fitness, vision to play either position equally well. Wherever he chooses to play he is destined for greatness. I think if you're reasoning honestly, whether you're adamant that he should play fullback or adamant he should play 5/8, nothing I've said in the preceding sentences should be controversial.
There are three questions to which the answers should determine where he should play, each of which have differing levels of primacy. They are;
1. Where does he want to play?
2. Where is best for the club?
3. Which position yields the fewest great players?
To answer question 1, I think it is clear that at this stage the kid wishes to play fullback. However, he has made a few comments that suggest he is open to a switch at some point in his career. That said, he has expressed unambiguously that (at least for the time being) he sees himself as a fullback.
Verdict on this point: Ponga to stay at fullback.
On question 2, the answer remains the most uncertain. There is no doubt Connor Watson is a wonderful young footballer. He has done some fantastic things playing 5/8 this year. However, he has also shown that there are areas of his game that he truly needs to work on if he is to make a complete first grade 5/8 (his kicking and passing). Some have argued that Watson would be better suited to fullback than 5/8 because of his playmaking deficiencies. This is an illusion, at least I would argue. Every good team in the modern game has a fullback who has excellent playmaking skills. The pass selection of fullbacks is absolutely crucial, perhaps more so than the modern 5/8's. In the modern game it is often the fullback who throws the final, crucial pass in organised set pieces. I don't believe that Watson is suited to that role, at least at this stage in his career, and regardless of where he plays this is something Watson should be working hard on in the off-season and at training.
So to be honest, after objectively looking at the side we have and weighing both sides of the argument the answer to question 2 remains unclear. One could argue that the answer to question 1 feeds into question 2 because we should keep Ponga happy by allowing him to play where he chooses (which as previously stated, appears to be fullback at this stage).
The answer to question 2 changes depends largely on our squad. If we suddenly signed a boom fullback (i.e. Matt Dufty) I would probably err to moving Ponga to 5/8. Equally, if we signed a boom 5/8 (i.e. Maloney) there would and should be no hesitation to leave Ponga at fullback.
The issue is complicated by the fact we have two players (Ponga and Watson) who are seemingly capable of playing both positions.
Verdict on this point: Ponga to stay at fullback and Watson to be given longer in the 5/8 position.
3. If one is to argue for Ponga to move into 5/8, I think this is the strongest line of argument to take. Outside of Maloney, Widdop, Thurston (if you include him a 5/8) there isn't a great deal of truly great 5/8s running around. This obviously depends on how define a "great 5/8". However, I think objectively you could argue that there are more great fullbacks in the game. Just look at the NSW and QLD sides, each side had at least 2 specialist fullbacks in it each game (Holmes, Slater and Trbojevic, Tedesco) and only one 5/8 (and I would hardly call Munster a great 5/8).
Verdict on this point: Ponga to 5/8.
So I think a fair conclusion, is to allow 1.Ponga 6.Watson 7.Pearce more time to develop.
The 3 circumstances in which we should think about moving Ponga to 5/8 are:
1. Ponga decides that is where he wants to play
2. 1.Ponga 6.Watson 7.Pearce is given a solid 12months together and doesn't work
3. We sign a boom fullback
So at this stage, our best side has Ponga at fullback