After being asked to field first after Hampshire won the toss, both opening bowlers make an impact early on with Chris Rushworth making the breakthrough in the sixth over, when Jimmy Adams (8) top edged a delivery to Scott Borthwick at square leg with the Hampshire total at 20.
Onions claimed the second wicket of the match three overs later with James Vince (2) caught at mid off by Dale Benkenstein.
Mitchell Claydon picked up two wickets in consecutive overs, bowling former Durham overseas player Neil McKenzie for 9 and the scalp of Sean Ervine (1) thanks to a cracking catch from Phil Mustard, who dove to his right to hold on to the ball to reduce Hampshire to 59-4 in the 16th over.
The visitors passed the hundred mark in the 25th over with Howell going on to reach his fifty shortly after (from 71 balls and including four fours).
Chris Rushworth claimed the fifth wicket, that of Liam Dawson, who was trapped lbw for 38 with the total 127-5 after 30 overs.
Ben Stokes, bowling from the Lumley End, brought about a quick end to Dimitri Mascarenhas’ return to the Hampshire side after injury after he was bowled for just 9. The nineteen year old then went on to claim the wicket of Benny Howell (66) after he chipped the ball straight to mid off bringing Bates to the middle to join Cork with Hampshire 155-7.
Stokes finished the innings with four wickets to his name after bowling Bates (2) and trapping his England Lions teammate, Danny Briggs (1) lbw.
Hampshire were all out for 161 after Claydon claimed the final scalp, with Cork (6) nicking the ball to Mustard.
The Dynamos lost Mustard early on after an impressive catch behind the stumps from Bates off Dimi Mascarenhas, who was sharing the opening bowling attack with Simon Jones, saw Durham 16-1 at the end of the second over.
Mascarenhas claimed the second wicket in the sixth over with Bates catching Mustard (5) with the total at 22 and went on to bowl Coetzer for 15 in the 10th over.
Gordon Muchall (67*), who has performed consistently well in the competition, and Dale Benkenstein (60) both looked untroubled in their innings, putting on a diligent 125 and both achieving fifties within one over of each other, to see the Dynamos home, securing two points for the win.