There isn't any inherent difference (indeed, you can do some coarse gravity surveys by basically watching the drift of an IMU relative to GPS), but there's a pretty big difference in terms of the parameters of your sensor. Most gravimeters don't make for good accelerometers and vice-versa. One of the biggest reasons being dynamic range: most gravimeters are only able to sense a very small range around 1g, which means they quickly saturate when there's any significant motion. I don't know if that's something which these quantum sensors can work around, however. (Also, you need a gyro good enough to go along with those accelerometers, which may still be a challenge)