Is it better to use cat, dd, pv or another procedure to copy a CD/DVD?

Background

I'm copying some data CDs/DVDs to ISO files to use them later without the need of them in the drive.

I'm looking on the Net for procedures and I found a lot:

I don't know if all of them should be equivalent, although I tested some of them (using the md5sum tool) and, at least, dd and pv are not equivalent. Here's the md5sum of both the drive and generated files using each procedure:

md5 of dd procedure: 71b676875b0194495060b38f35237c3c

md5 of pv procedure: f3524d81fdeeef962b01e1d86e6acc04

EDIT: That output was from another CD than the output given. In fact, I realized there are some interesting facts I provide as an answer.

In fact, the size of each file is different comparing to each other.

So, is there a best procedure to copy a CD/DVD or am I just using the commands incorrectly?

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More information about the situation

Here is more information about the test case I'm using to check the procedures I've found so far:

isoinfo -d i /dev/sr0 Output: https://gist.github.com/JBFWP286/7f50f069dc5d1593ba62#file-isoinfo-output-19-aug-2015

dd to copy the media, with output checksums and file information Output: https://gist.github.com/JBFWP286/75decda0a67605590d32#file-dd-output-with-md5-and-sha256-19-aug-2015

pv to copy the media, with output checksums and file information Output: https://gist.github.com/JBFWP286/700a13fe0a2f06ce5e7a#file-pv-output-with-md5-and-sha256-19-aug-2015

Any help will be appreciated!

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