Here are the six I know about. The scan is of the front and inside of all the books put into a single picture so the lower right match on the front scan is the lower left match on the inside scan.

The biggest difference is what is on the front of the blue match cover. Most you will find have the windmill on the back.

Scarcer still are the matches with the "white horse" on the back next to the windmill. These pale horse books also have every other match stick printed with the hotel name rather than just being blank blue sticks. These also happen to have the background of inside of the cover brown rather than blue.

The hardest to find are the matches with a desert scene on the back rather than the windmill. I've only seen about a half dozen of these.

There are also seven other front-striker matches for El Rancho Vegas that are not features. Finally, there is one cover that lists inside all the hotels that Thomas Hull owned; the one in Las Vegas, the one in Arkansas (Arrowhead Hot Springs), and the seven in California. The hotels he owned in Sacramento and Fresno were also called "El Rancho".

It's been a few years since I looked at the varieties of this feature match. If anyone knows of still more varieties, please post their scans here.