The Windows PE method is a nice one. I use that method since a couple of years ago. I used to use my own Windows PE with my own customizations that fits my needs.
The unique problem with that method is that you've to spend a good bunch of hours reading tutorials and testing things before getting things running the way you need or like. Also, you're forced to use an optical drive or, if you want to boot it from a USB drive, you need to read a new big amount of documentation and tutorials to get it working and with the posibility that you can get some errors too.
We can say that the Windows PE method is flexible, capable to add new tools that can help you on your work, but is hard to get, needing lot of hard work and testing.
The booteable USB method is very very fast, letting you to prepare a disk that can be used for installation in just a few clicks and minutes and don't even using a single CD or DVD, but it doesn't let you do another thing apart from running the Windows 7 installation in a very high speed in most cases.
Is up to you if you can spend some time getting a nice toolkit or if you just need to install Windows fast and easy.
Hope it help you to decide what you have to do.