Core aerate and overseed or slitseed?

[danhalen]

My lawn is well established (7 years) and has been very thick up to this point. There are some thinning areas that need some attention. I cut it short today, dethatched and collected the thatch. Now I want to overseed (pricey bluegrass mix from seedland.com). I'm located in the Midwest. Is one option better than another?

[KS_Grasscutter]

I like to aerate and seed, just for the added benefits of the lawn. But if there is no/very little thatch, and no compaction, aeration isn't really necessary IMO. Plus, conditions have to be PERFECT for aeration to work just right (which happened on the lawn I aerated today, somehow the soil was JUST RIGHT, pulled like 3" plugs with my Bluebird aerator).