The AC in tinyAVR 1-series has two modes: Fast mode and Low-Power mode. In Low-Power mode, the power consumption is reduced, and the propagation delay is approximately 150 ns. In Fast mode, the propagation delay is reduced to approximately 50 ns.
The AC in tinyAVR 0-series only operates in Low-Power mode. In addition to this, on the 16 KB devices, tinyAVR 1-series has three ACs, and more inputs are available.
On devices with 8 KB of Flash, there is a difference in the base address of the AC. On tinyAVR 1-series, the base address is 0x670. On tinyAVR 0-series, the base address is at 0x680. As long as the project being migrated is compiled with the correct device header file, this may not be a problem.