What format is best for my games?

[blueblur22]

I have riped a few of my games using 2 different methods. The 2 resultes were 1) ISO and 2) GCM.

Are one of these 2 files faster or more efficient to play? The GCM format games seem to run with higher fps then the ISOs, but I wanted an official opinion.

Also, are there any other formats that may be even more efficient to use?

LASTLY, does anybody know a simple method to convert various GameCube games into whichever the best format is?