Fundamentally different. Unlike old one it’s purely a bilateral deal NOT within NATO framework, i.e.

It’s completely independent of NATO. NATO will have no control, no business to do with US military in Greenland.

Old deal: U.S. military presence in Greenland is because of NATO (both Denmark and U.S. are nato members). Legally if NATO say no, U.S. can not build military bases there and can’t add new military bases without permission of nato (permitted by every nato member)

New deal: U.S. can do whatever they want permanently on military presence in Greenland.