Hmm, further testing.

Unit A: Dismounted Noble Knight, has upgrade path 4, 5. Has armor level 8 at upgrade 4: average losses vs archers: 22.
Unit B: Dismounted Noble Knight modded to have upgrade path 1, 2, 3, 4. Has armor level 4 at upgrade 1, theoretically armor level 8 at upgrade 4: average losses vs archers: 12.

Unit B with the gold upgrade more resistant than Unit A, though both should be identical in theory, with level 4 armor and armor value 8.

Have tried the same with other units.