They look like the same model tank to me, the 99A. I thought we have only seen the 99A2 as a prototype with a much bigger turret, or thicker add on armor. While the original 99 is the model with the chunky laser dazzler.
They are the same vehicle. The correct designation for that vehicle is ZTZ-99A. However, there are two different variants of the ZTZ-99 so some observers are tempted to call one the ZTZ-99, the other ZTZ-99A, and the
actual ZTZ-99A in the pictures above, the ZTZ-99A2.
Chinese BBS usually refer to the later version of the two ZTZ-99 variants as the 99改 and the ZTZ-99A (or informally A2) as the 99大改. They respectively mean, 99 improved and 99 greatly improved.
Alternatively, they refer to the earlier 99 variant as the 99一期, the later 99 variant as 99二期, and the 99A as 99三期. They respectively mean, 99 first edition, 99 second edition, 99 third edition.