Well First off lets see each:
-High Sp. Atk
-Decent Sp.Atk and Atk
Competitvly Seperior is better as a staller, and with wring out it becomes even better. Lilligant ends getting outsped by most of the Pokemon, which does do to well when battling fast and powerful flying types.
But since you are talking about an in game team I would still go with seperior, since having 2 grass types does not do you too well and I did just fine with serperior in my walkthrough of B2.