FMCSA or Federal Motor Carrier Safety Administration has listed the major differences between the older e-logs/AOBRD and the modern ELDs here. Both technologies require to be plugged into the vehicle to retrieve important data. However, ELDs are more advanced, and document more information. They also allow for transfer of data during roadside inspection.
Another difference is in presentation of data as laid down by FMCSA. The newer ELDs can present data about driving hours, change of duty of a driver, and more in graph and grids. This wasn’t possible with older AOBRDs.
One of the biggest and most important difference between the two technologies is the records of edits. AOBRD allowed drivers, operators and others to make changes in the records that weren’t documented. To make the data authentic and accurate, ELDs allow edits, but also retain the original data. ELDs keep a track of who made the edits and when. This prohibits any discrepancy in the data collected, and makes drivers and operators accountable.