AnTuTu has become one of the more popular benchmarking tools when it comes to Android devices. Each benchmark test result is uploaded to a database, which is compiled for quarterly reports. This is done in order to keep the comparison charts up-to-date.
The major version upgrade from v5.0 to v5.5 mainly focuses on accommodating devices with 64-bit architecture. This is an absolute necessity with the inrush of 64-bit devices from various manufacturers.
Aside from the 32-bit and 64-bit test distinction, there have been updates to the 3D tests, and the overall user interface. Some are still generating bug reports when it comes to the 3D benchmark tests, as it causes crashes for certain devices.
The AnTuTu team has responded punctually to the crash reports, and are ironing things out.