Making a Bart PE disk is both more and less difficult than making a nLite disk. It is easier because you can make an image immediately, using no additional parameters. However, to actually make a useful disc, there are substantially more steps involved.
I was going to do a tutorial on this, but I do not have the time. Instead, I will add a few highlights.
Bart PE is a live install, which means it installs to RAM, but runs like a fully operational OS. Because it also has full network support, it allows you to install an OS to a computer from a remote location. What is the advantage of this? Well, lets say you have two or more domains that clients must be configured for, and multiple brands of workstations. How will you fit all of that on a single CD, which only has enough space for one OS?
The answer is to put multiple images on a server, and add a file browser to Bart PE. Simply choose the image you wish to install from the server and run with it.
nLite is great for convenience, but if anyone ever steals a CD, your CD key and any pre-installed software is now compromised. Simply stealing a Bart PE is but a single step in several more requirements. First, none of the images are stored on the disk, so you must have a password with permissions to access them. If the thief manages to do this, and install an image, they will still need a viable domain logon. If they change the admin password, they have only been able to get a free copy of XP (through a lot of work) but still don't have access to any data.
While this is far from unbreakable (there are several ways around the security) it is still better than no security at all.
You can preload some diagnostic tools, virus scanners, and other useful third party tools. These can be run from the live install, in the even that the computer won't boot. This can greatly simplify the troubleshooting process, saving hours of work and therefore money.
Because the image is not on the disk, it can be updated, removed, and new images added without any changes to the Bart PE disc. This is a great boon for administrators that do not want to waste time re-creating restore discs.
Bart PE is not perfect. It requires knowledge of passwords, domain names, and image types. This means installation takes longer and should only be performed by qualified personnel.
Furthermore, because the images are installed over the network, a server must be dedicated for this purpose and enough bandwidth must be reserved. Smaller companies may find this more difficult, and it further increases the amount of time required for an install.
I did find a tutorial that was already created.