I am going to assume your Serperior is physical, so go for Leaf Blade. However, consider replacing Aerial Ace with Leaf Storm because most of your opposing Grass types are also going to be Poison types, and you aren't supposed to stay in on a Bug type anyways.
Besides, it's a rather weak move. Leaf Storm is much more powerful and might just allow you to plow through a physical wall that a physical Serperior would attract.
Hope I helped!