But there was a particularly intense exchange over climate change and farming, where Collins praised the agriculture sector's importance to the export economy.
"Understand this: there is no free lunch for us in this world. We are a little country that has to fight for every trade deal," Collins said.
"We need to wake up ... we have to pay for health, we have to pay for education."
Ardern retorted that farmers were already playing their part in the climate change conversation, making New Zealand a world-leader despite the country's relatively tiny contribution to global emissions.
"Unless we move on this, we will be left behind and we will lose our brand. Dairying is doing well ... as we work on these environment issues together.
"It is a sad day when give up on our reputation of being clean and green.
"We have the potential to export green energy. The opportunity here is enormous for us."
Ardern repeatedly asked Collins what National's plan was on climate change, and Collins said the tech sector was the single biggest game-changer.
"I don't know how data centres are going to help climate change," Ardern said.
Collins: "You don't understand technology if you think it's a data centre. I should take her to some tech places."
Collins put an emphasis on growing the economy through on a number of policies including National's temporary tax cuts - described by Ardern as "an unaffordable sugar hit".
Ardern's opening and closing statements centred on the Covid response to sway voters to pick stability, adding that change could upset the gains New Zealand had already won.
She said her often-used line of going hard and early, prompting a reply from Collins that Samoa had gone a month earlier than New Zealand.
When Ardern said that wasn't correct, Collins said: "Actually, don't disrespect Samoa."
Collins said Ardern was being "ridiculous" during an exchange over lockdowns, saying the second lockdown would have been avoided if border-facing staff were being tested as they should have been.
"I'm not going to have Ms Ardern stand there and just reinvent history," Collins said.
When Ardern said there was no evidence that the outbreak came from the border, Collins said: "Where did it come from? A rock in your garden?"
Ardern then pressed Collins on the $800 million for new spending in its first year budget, which she said was simply not enough to cover what a Covid-world might throw up.
"What will it [National] cut?" Ardern said repeatedly, to which Collins answered that nothing would be cut.
When they were asked questions from viewers, Collins wouldn't say if National would ban gay conversion therapy, which is Labour's policy, while Ardern wouldn't say how she voted on legalising cannabis, which Collins is against.
Collins defined "wokeness" as a "lot of nonsense", while Ardern said it meant "huge self-awareness".
They were then asked about the cost of living and the price of ordinary goods. Both were spot on for the cost of Netflix, but wide of the mark when it came to the price of two litres of milk and two kilos of lamb.
Both leaders agreed that it was too soon to move to a republic when the Queen dies, though Ardern said she thought it might happen within her lifetime.
Before the debate, Collins had been on the back foot following a leaked email from National MP Denise Lee.
Collins had said on Monday morning that she wanted to review Auckland Council, prompting an email from Lee to the caucus calling Collins' comments "highly problematic" and a "nightmare".
Lee added that for Collins to bypass her when it came to a policy for which she is the spokeswoman showed "incredibly poor form and displays a shockingly bad example of poor culture".
Collins said the Auckland Council issue was something the campaign team has worked on for weeks, and she had spoken to Lee about the email.
Lee released a statement yesterday saying that it was an internal email, and she accepted Collins' decision about the policy and unreservedly supported the leadership.
After the debate Collins again defended making "leader's calls" on the campaign trail, saying it was nothing unusual.
Collins thought both she and Ardern had done well and politics was the winner.
Ardern again declined to pick a winner.
There is one more leaders' debate, moderated by TVNZ's political editor Jessica Mutch McKay, which takes place next week.
