They all offer pipeline and other energy infrastructure data (transmission, gathering, etc.), separated into geographic regions (some use states, others groups of states). The pricing was similar, they were all within 10% of each other if I remember correctly, you pay per region/state for the data. The main thing was the licensing: you can't purchase the data outright, only license it annually. If you do not renew the license, you are required to destroy all the digital data and any data derived from it. You can keep any finished paper maps/PDFs. They all had license terms like this.
They all offer sample data downloads so you can get some idea of what you're buying, as well as data dictionaries so you can see the data fields they use.