Ryan Macbeth's five wicket haul had put the competition favourites very much on the back foot as they were reeling at 56 for 5, with captain Stephen Doheny (0) and the free scoring Jamie Grassi (4) both back in the hutch.
Sam Murphy hit a patient 21,before falling to impressive spinner Aaron Heywood (2-16 off 10).
Danny Hogan (36) and Fionn Hand added 47, and it was the North County man who shephered the tail to get the Southern XI up to a respectable 171 for 9.
He hit 6 boundaries in a top score of 46 and you felt that those late order partnerships could prove pivotal against two evenly matches sides.
MacBeth finished with the excellent analysis of 5 for 31, while all-rounder Ross McCay picked up 2 for 31.
Left-armer Josh Little removed Mattie Barr (4) early on, but a second wicket stand of 57 between Graham Kennedy (31) and Ross Dougherty (27) looked to have set the NW on course for the title.
However the spin duo of Conor O'Gorman (3-27) and Stephen Doheny (3-22) turned the contest on its head as five wickets fell for just 13 runs.
The NW tail wagged and a tenth wicket stand of 36 between Ryan MacBeth (25*) and Billy Dougherty (12) got the NW agonisingly close before Hand fittingly had the final say as he dismissed Dougherty.
Cricket Ireland President Dr Murray Power paid tribute to both teams for an absorbing contests played in a superb spirit. He also thanked Coleraine and Drummond for the hosting of the event.
Ireland U17s are in action next week when they play Irish Schools in Belfast on Tuesday and later in the month have a three game Challenge Series against The Netherlands.
Full scorecard here