If one part of the solid stream (like part02.rar ) is corrupted, it may be impossible to extract any files that follow that damaged area in the sequence.

Extraction speed is not affected if you are unpacking the entire game at once. Managing Your Multi-Part Archive

To extract just one file from the middle of the archive, the software must analyze and decompress all preceding data in the stream.

How to create solid archives in Winrar Step By Step Tutorial Mayank Agarwal (EasyVideoSeries) YouTube• Mar 2, 2012

Treats all files as a single block, reducing redundancy and resulting in a smaller overall download size.