Ripping questions . . . Why as Why?

[spmc]

I'm a computer/DVD newbie. When I am successful with something on the computer it is usually because I blindly follow instructions telling me do A, then B, then C. I don't ask quesitons and am usually happier for it. But this has been bugging me for awhile.
First. . . Why, when you rip a DVD, does it rip faster in ISO mode than in FILE mode? ISO mode rips average 8-12x. Same disc ripped in FILE mode only averages 3-6x.
Second. . . Why do some discs rip faster than others. Some discs rip fast 10-12x while others rip slow 2-4x. They are all about the same size. There seems to be no difference whether they are encrypted or not (some of the slowest rips are home movies I authored), or whether they are single sided or double. Why the speed difference?
I have read all the rip tricks and settings and feel confident that I am in step with all of them.
I am not expecting 16x rip speed from every disc, I am just curious as to why the differences.

[Gazorgan]

Your speeds are about right.

Double layer disks rip slower. Disks with a lot of errors rips slower. Poorly pressed disks rip slower (old flipper disks can be like this).

ISO mode is just copying what's there, while file mode takes a VOD and splits out the M2V's and sound tracks (think of it as copying a ZIP file versus unZIPPING the same file). If you are jsut ripping the main movie, there is a lot of extra stuff that has to be ignored, but still read through.

My old DVDROM was locked at 2x, but evey 6th rip or so it would fly at 4x....go figure.

Things like your virus scanner, level of fragmentation on your harddrive (this is a biggie!!!!), background programs, background programs you don't know about, etc.

[spmc]

Thanks for the answers. I understand the ISO/FILE thing now. I kind of figured it was something like that.
As for the other rip speed variances, I guess it is just a combination of all the things you mentioned. It's just strange. I can rip a non encrypted single layer discs with 3Gb on it at 3x. But then a dual layer encrypted discs with 8GB on it rips at 12x. Crazy.
Guess I am just wondering where the consistency is.
Thanks again.