I think the simpler the movement possibly the less there is to go wrong! But then the 2824 would be for the non-chrono Seamasters, and the A7750 would be for the chrono versions.
You'll have to service a chronograph (7750 movt.) more often than a regular ETA 2824 movt. With that said, the 7750s are still solid movements and I'd say get the chrono in the case of the seamster. Are you referring to the 300m or the Planet Ocean?
In case of 300m SMP, get the chrono; its a fantastic rep.