Crits not considered here (since a crit is always a 2HKO)
WG x2:
With 5 Sp. Def (6-/x/x) (3.5%):
	255/256 (99.6%) with 9 Sp. Atk (31-/x/x) (16%)
	100% with 10+ Sp. Atk (x/0+/0+) (84%)
With 6 Sp. Def (7-31/6-/6-) (30.9%):
	31/256 (12.1%) (15x7, 1x9) with 9 Sp. Atk (31-/x/x) (16%)
	255/256 (99.6%) with 10-11 Sp. Atk (x/0+/0-19) (78%)
	100% with 12+ Sp. Atk (x/x/20+) (6%)
With 7+ Sp. Def (x/7+/7+) (65.6%):
	31/256 (12.1%) (15x7, 1x9) with 9-10 Sp. Atk (31-/19-/x) (58.5%)
	255/256 (99.6%) with 11-12 Sp. Atk (x/20+/0+) (41.5%)
HP has no impact for WG rolls since it never rolls 8. Therefore, 14 damage will always not be enough since the Pooch cannot have 14 HP and 16 will always be enough since it cannot have more than 16 HP.

Overall Kill Rate with WG x2: .00558 + .0294 + .00598 + .24006 + .01854 + .04643 + .27115 = 61.714% to 2HKO w/o crits

Tackle x2:
With 6 Def (29-/x/x) (15.0%):
	100% with 12+ Atk (x/0+/0+) (84%)
	With 16 HP (30+ IV) (0.9%):
		59.4% with 11 Atk (20+/x/x) (6%)
		0.4% with 10 Atk (19-/x/x) (10%)
	With 15 HP (29- IV) (14.1%):
		93.8% with 11 Atk (20+/x/x)
		9.8% with 10 Atk (19-/x/x)
With 7 Def (30+/29-/29-) (79.8%):
	With 16 HP (30+ IV) (5.0%):
		100% with 14 Atk (x/x/20+) (6%)
		59.4% with 13 Atk (x/20+/19-) (35.5%)
		0.4% with 11-12 Atk (20+/19-/x) (48.5%)
		0% with 10 Atk (19-/x/x) (10%)
	With 15 HP (29- IV) (74.8%):
		100% with 14 Atk (x/x/20+)
		93.8% with 13 Atk (x/20+/19-)
		9.8% with 11-12 Atk (20+/19-/x)
		0% with 10 Atk (19-/x/x)
With 8 Def (x/30+/30+) (5.2%):
	With 16 HP (30+ IV) (5.0%):
		59.4% with 14 Atk (x/x/20+) (6%)
		0.4% with 12-13 Atk (x/31-/19-) (78%)
		0% with 10-11 Atk (31-/x/x) (16%)
	With 15 HP (29- IV) (74.8%):
		93.8% with 14 Atk (x/x/20+)
		9.8% with 12-13 Atk (x/31-/19-)
		0% with 10-11 Atk (31-/x/x)

Overall Kill Rate with Tackle x2: .126 + .00032 + 0 + .00794 + .00138 + .003 + .01054 + .0001 + 0 + .04488 + .24908 + .03555 + 0 + .00178 + .00016 + 0 + .0421 + .05718 + 0 = 58.001% to 2HKO w/o crits

Conclusion: WG x2 gives you ~3.7% more likelihood to 2HKO the Poochyena, however, -Attack plays a large part into the Tackle rolls being downgraded so you may be able to get an indication of your stats by Tackling which may be worth the slight dip in likelihood.