I've tries to google and find some side by side trials that might show some results comparing each method.
Seeding for us is still months away but I'm curious the difference in time it would take to do both methods. If they were about the same I wouldn't mind trying a few smaller lawns. It could serve as a good way to compare even if it wasn't the same lawn.
I have quite a few who probably don't irrigate properly or have very thin or bare lawns by reseed time. If I could get them to do slit seeding then my hope is that the seed to soil contact would help germination.
At a machine cost of $2000 it would be a pretty large investment for someone who only seeds 125-200k of turf....mostly which is seeded via core aeration.