My comparison between the two are as follows.
Common: both are calendar sport watches, with practical water resistance
Difference:
Dial: 5726 is easier to read, more contemporary. 5740G is more crowded and classic layout like 3940/ 5140
Profile: 5740 is slim, while 5726 is slightly thicker
Metal: 5726 is truly white stainless steel, 5740 is grey white.
Weight: 5740 is heavier
Cheers,
Henry