From the marketing materials the description of the FG-730 is as follows:
FG-730 from IntelliSense are dual technology glass-break detectors that use flex detection and audio discrimination to detect breaking glass. The flex and audio technologies are sensitive to different frequencies. The flex technology is sensitive to ultra low frequencies, the type generated by a blow to a glass window. The audio technology detects the frequency of breaking glass. The audio technology remains off until the flex technology detects a blow to the glass. For an alarm condition to occur, the audio must detect the frequency of breaking glass within a defined time-window after the flex detects a blow to the glass. Because both technologies must detect and verify glass breakage, false alarms are virtually eliminated.
Where did you see the same description for the FG-1625?
If you are convinced the FG-1625 is better, by all means get it. I'm sure it will work fine for you.