The Delta website does quote a different range for the two, I believe:
*
https://www.delta.com/content/www/en...200er-777.html
*
https://www.delta.com/content/www/en...200lr-77B.html
You can see a slightly different config (one more Galley) as well as slightly different dimensions/wingspan/range, etc.
I believe the actual pax experience is nearly identical now that they have the same seats, etc.
It looks like there's an extra space in 'Seat Width/Pitch' as well (
89 cm) on the 77B