The tourists lost 21-15 in Rosario in the first Test match but Hadden was most impressed by the progress made by his forwards against the world-class Pumas pack as they fought back to win the second Test 26-14 in Buenos Aires on Saturday night.
It was only Scotland's second win on Argentinian soil and the first since 1969.
"I think that the tour was positive, but the bottom line is we needed to win further for it to be a positive experience," head coach Hadden told PA Sport.
"It is hard to be positive when you play well and lose. You have to get the confidence and self-belief you need to make progress."
Hadden was delighted to have ended a seven-match losing streak to Scotland's bogey team, with his side's last win against the Pumas home or away coming as far back as 1990.
"We had never beaten Argentina at junior levels, under-19, under-21 and we had only one win against Argentina in a full cap," he said.
"So, obviously, we are very proud. A lot of the games were very close, so maybe we had our reward because of these close matches.
"Argentina are a thorn for everybody. Everybody finds it difficult to play against them, because they are a very strong rugby-playing country."
He said: "When we arrived, the areas I was concerned with were the set pieces. I think we got the better of the scrummage and we got the better of the driving maul.
"I knew these were the two areas that Argentina take a lot of pride in and we knew we had to attack these areas and we were determined to prove that we can match them in these areas.
"I felt that if we could match them in these areas there would be other parts of our game that would give us some advantage in the Test matches.
"We had struggled in these areas against Argentina in the past, but we've done very well now."
Hadden, 53, added: "We did better in the breakdown. But we improved the defence, the penalty count, which is always very important.
"Another difference was that Argentina had luck last week, we had luck this week. In a very close match, everybody needs a bit of luck."