The answer is Hadlee - but not by as much as you might think.
Hadlee had taken 225 at an average of 24.55, while Wagner has 212 at 26.32 for the Black Caps.
Here is another tester. Hadlee took the new ball. Wagner has had to do his best with the old ball and against batsmen with super-sized bats.
Arguably, the 34-year-old South African-born left-armer does not get the credit he deserves in his adopted home.
The statisticians love him, though. Wagner is the ICC No2 ranked test bowler.
He bumped England’s Stuart Broad down a spot with his six-wicket haul in the first test against the West Indies last week.
"I think it is a little bit of a reflection of obviously having some good form of [late]," Wagner told media when asked about his new status.
"But at the same time it feels a little bit unreal," he added, suggesting there were a lot of quality bowlers sitting below him who could be ranked higher.
"Some of the guys who are playing all three forms are very skilful and do a hell of a lot better than what I do."
Wagner will notch his 50th test in the second test against the West Indies at the Basin Reserve beginning tomorrow.
West Indies seamer Shannon Gabriel will also reach the milestone.
Wagner moved from South Africa to Dunedin in 2008 to pursue his dream of playing international cricket.
The former Otago player had to wait four years while he qualified and sometimes still has to pinch himself.
"It is pretty surreal. I’m getting goosebumps at the moment just when you mention it.
"It is quite emotional. All the sacrifices and everything you’ve done to be here and to finally play 50 test matches means a lot.
"I never thought I would get there. There is a lot of hard work that goes into it and it is a pretty special feeling every time you put that black cap on your head."
The Black Caps recorded a very comfortable win in the first test but that does not mean the side will relax before the second.
Wagner expects the West Indies’ batting line-up will be better prepared.
"They’ll definitely come harder and they will work on those [batting] plans. This is test cricket, you expect that."
Wagner has nine five-wicket bags at test level but he is in a reasonably exclusive club of bowlers who have taken 200 or more test wickets but have not taken 10 wickets in a match.
That list includes Joel Garner, Brett Lee and Morne Morkel. They all had some very stiff competition down the other end.
Wagner has Tim Southee and Trent Boult taking a whole lot of wickets as well.
And since we have compared Wagner with Hadlee, it is worth noting Hadlee, who had Ewen Chatfield down one end for most of his career, took 10 wickets in his 50th match.
A 10-for would be a nice way for Wagner to celebrate.
Wagner: his top five hauls
Former Otago left-armer Neil Wagner will bring up 50 matches for the Black Caps in the second test against the West Indies which gets under way at the Basin Reserve tomorrow. Cricket writer Adrian Seconi ranks Wagner’s top five performances.
Working over Smith
4-83 & 3-50 v Australia, Melbourne, 2019
Wagner was the only New Zealand bowler to emerge from the tour of Australia having enhanced his reputation. The lionhearted left-armer bounced his way to success against the best since Bradman. He captured Steve Smith’s wicketfour times during the series. Watching him work over Smith at the MCG was a treat. Turns out Smith does not like the ball hurtling towards his rib cage either.
Finding a crack
4-64 & 4-62 v India, Auckland, 2014
Need a wicket - Neil’s your man. Brendon McCullum blazed a double ton but Wagner sealed the tense win with amighty effort with the ball. He got the key wicket of Virat Kohli in the second innings and removed MS Dhoni twice.
Wonderful Wags, woeful Windies
7-39 & 2-102 West Indies, Wellington, 2017
Wagner decimated the West Indies batting line-up on the opening day to set up a test win. It is quite a sight watching him celebrate and he got to do it often during a man-of-match spell which was as good as you will see. Statistically, it was his best return in an innings.
Final stretch
3-90 &5-44 v England, Mount Maunganui, 2019
Wagner probably has more energy left on day five than any cricketer ever born. He summoned all of it to run through the England lower order and bowl the Black Caps to a tremendous victory.
Wagner the lionhearted
4-42 & 3-141 v England, Dunedin, 2013
Our favourite South African established his reputation as an inexhaustible seamer early in his international career. Game four in fact. Everyone in Otago knew how reliable he was. But the world found out as they watched him bowl his heart out for 43 overs in the second innings.
