Here’s a good rule to use when deciding on T-track versus threaded inserts. (OK, its two rules, but they are the same rule. 
)
If the majority of your parts are large compared to the grid, you’ll prefer threaded inserts.
If the majority of your parts are small compared to the grid, you’ll prefer T-track.
Why is this? Granularity.
Many times I fight for a threaded hole to use for my clamps on small pieces. My grid is from the Myers wasteboard and is 2". They don’t line up just right with the length of my clamps. Then I’m thinking the T-track would give me more granularity in adjustment locations.