LME or DME as late addition

NB kits specify the LME as late addition.
Brewers Best kits specify the DME and Dextrose as late addition.

The recipes seems to be designed around these late additions for bitterness, color etc…

Which is more effective as a late addition or does it matter?

I have used both and I don’t think it matters if you are careful. The only issue I would see between the two types of extract is that LME will fall to the bottom of the kettle when you add it. As long as the LME is added with the heat off (assumes a propane burner) or removed from the stove top, you should be OK. Removing the kettle from the heat source will reduce the likelihood of scorching the LME. Stir well after you add to ensure proper mixing.

In my experience, this did not happen with DME.

Hope this helps.