if memory serves me right, there are other differences too:
case:
the 7753 came in what was known as the "new cases" while the 7750s used the "old cases". w regards to difference, the profile of the bezel is different, the machining on the old is supposedly better than the new, CGs shaped differently, lugs shaped slightly differently, etc. mostly aesthetics. the "new cases" were generally regarded to be inferior to the old ones cause the old cases look closer to the gen. personally, after handling both, there aren't that much of a difference quality-wise. however, the old cases do feel better machined and heavier, the sapphire seemed thicker as well (rises higher above the bezel)..the different cases was because they were sourced from different factories, ie factory A produces 7750 only and factory B produces 7753 only. there were batches of 7753 powered daylights using the old case but that was eons ago, in the 196/188 generation, before the 250s even existed.
dial:
the cutouts for the dates are located at a different positions and the datewheels are of different depths. imho the dial of the 7753 has a more balanced layout wrt date positioning and, with the datewheel much closer to the dial, looks so much better than the 7750.
