Most good modchips allow you to boot games at 6x, rather than 3.4x, which is the speed of the backup loader or disk channel boot with Preloader.
This will allow you to run games at full speed, as if they were original copy games.
The Wii's drive is underclocked to 3.4x when reading DVDs.
Much more isn't required to play a movie, but these are games, which would require 6x.
The Wii Optical disks are printed with a serial that the Wii Reads to know to show them in the disk menu without any modifications, and then run the game at 6x speed, rather than reading it as a DVD- 3.4x speed.
Hope this helps you =)
Purchase the modchip. It's worth it, but be careful with the installation.
I'm not sure if Nintendo would renew your Wii if you have warranty due to an unsuccessful system modification.