Of course this was an academic debate to some degree. Wenger didn't want the Dutchman to go anyhow, let alone to one of his Premier League rivals.
His biggest dread was that his former captain would join the exodus to Manchester City: Adebayor, Kolo Toure, Nasri, Clichy. Van Persie would have been the last straw.
In the end, it was Robin who made clear that he wanted to go to Manchester United even though it was probably for less money.
Arsenal have been declining slowly for a few years now. There are players there whom Wenger would surely not have countenanced even a couple of years ago.
Sitting watching them last Saturday lunchtime, it was hard not to compare them adversely to the record-breaking Arsenal side at the turn of the century. There was no finesse or punch and especially no leadership.
Van Persie at Arsenal
It is clear now how much Robin van Persie gave Arsenal particularly last year. Wenger deserves the utmost credit for taking a player who was essentially a left winger, who could play in the hole or as a target man, into a striker.
The intention was for him to replace Denis Bergkamp, also a very intelligent footballer. But with the exodus of players in the last few years, especially Fabregas, the need was for an out and out goalscorer and a captain.
And van Persie certainly led by example last season. Remaining the most injury free since he joined the Gunners, he played his greatest number of games (48) and scored almost twice as many goals as in any previous season (37).
In fact it seems hard to understand how he hasn't been a striker all his life.
It is quite clear that without him Arsenal would have been in trouble last year. OK so they finished third, but they were only six points ahead of Chelsea in sixth place. And as we know, they haven't won a trophy for seven seasons.
So it is clear that from Arsenal's point of view van Persie was critical to their success of any sort.
But is one season enough to conclude that being at Arsenal got the best out of the player himself?
RVP at Manchester United
Yes, he is now 29. Some might say that he is past his best, but others think strikers mature in their late 20s.
This player seems like he is still growing and evolving, and if there is any place to do that it is at Old Trafford. Apart from meeting the team's needs, every player that comes into Manchester United gets better, except the ones who shouldn't have been signed in the first place.
One of the interesting things that have emerged in the last week or so has come from the discussions about the blossoming partnership between Rooney and van Persie.
Asked about who should play as the out and out striker, the Dutchman characterised their joint role as two "nine and a halfs".
This is very much in keeping with the apparent fluidity and interchange of roles that Sir Alex is getting out of his attacking players. So the two senior strikers take it in turns spontaneously swapping as No.9 and No.10.
It's working well so far. Between them, they have fourteen goals and ten assists so far this season, virtually all while the two have been on the pitch together.
In fact, neither Sir Alex nor Wayne himself seem worried that he isn't scoring as many goals as Robin. For them and the rest of the squad it's the team and the result that matters.
And van Persie is a team player, beyond question. Coming from a teenager that Sir Alex decided not to sign because of his immaturity, through a hothead who got sent off and was benched for a period before he settled down at Arsenal, he is now an unusually mature man and footballer.
So Is He Better Than at Arsenal?
It's early to say, but instinct says yes.
Last season, Van Persie and Rooney were the Premier League's top and second goalscorers. The only question was whether they could play together and form a synergistic partnership.
That question has been answered by the stats mentioned above, but also by this analysis which puts Rooney top and Van Persie second as top-rated strikers in the Premier League.
His performance so far for United is at least comparable to that at Arsenal. Last season he was the most influential player from the top eight teams.
Pro-rating his performance so far for United, he is well on target to at least match that. He has eight goals and three assists in 10 appearances, which pro-rates to 30 goals and 11 assists for 38 matches.
So assuming he stays fit, he is already delivering the goods.
But anyone who watches Manchester United will tell you that he is much more than his own personal statistics.
His new team scored a total of 89 goals in the Premier League last season, of which Wayne Rooney got 27. Sir Alex is confident that he will get at least 20 this season.
Now you can't simply add van Persie's goals to last season's tally and come up with 119, but if he does get 30 and Rooney gets 20 you're looking at the highest scoring team in the League. No wonder Sir Alex is so insistent that United won't lose the title on goal difference.
The things that preoccupied people earlier in the season were United's defence, the injury crisis, the conceding first and the general leaking of goals.
They have tightened up in defence in the last couple of weeks and one can reasonably expect that they won't have to score three times to come back and win every match this season.
It is very clear from the results so far, how much of an effect Van Persie has had on United. They're currently sitting top of the table after losing to Everton and Spurs.
But beyond that, two other factors suggest he will be even more valuable to United than he was at Arsenal:
He has had a galvanising effect on the team as a whole. No better was this illustrated than against Braga on Wednesday. He came on with 15 minutes to spare and scored a goal of individual brilliance. As Sir Alex said in his MUTV broadcast Presser, after that only one team was going to win.
The other effect, which we mentioned in the post-match review against Arsenal, is the effect on the crowd. Van Persie has stirred them mightily. He is already being mentioned in the same breath as Eric Cantona. He can drive them to success this season.
Finally, irrespective of other adaptations Ferguson has made, United have already at a canter qualified top of their Champions League group, with two games to play. Van Persie's contribution of three goals in four games has been a material factor.
It takes time to adapt to a new team. Also, Robin Van Persie had no preseason to speak of because of the continuing uncertainty over his transfer. When he arrived at Old Trafford he was nowhere near match-fit.
When you take all these factors into consideration, he may be the biggest single factor in the whole of the Premier League title race this season, as well as leading United to greater success in the Champions League. He is improving the players around him as a bonus.
The conclusion must be that his best years may be yet to come, including a stellar 2012-13.
If City had got him, the rest would have been playing catch-up. Arsenal's sad loss is United's game and as with Cantona, Robin van Persie may catalyse the next era of success and bridge the team into the next dynasty before he finally hangs up his boots.