I had the same choice last year. Exact same choice! Coming from Oregon and deciding on a home game vs. San Francisco or an away game at Arizona.
We chose to go watch the Rams at Arizona and it was an awesome experience. Felt almost like a neutral site game with maybe 30% or more Ram fans. The venue is awesome! Beautiful stadium and it looks like it has great views from almost any vantage point. Hotels and restaurants are within walking distance with plenty of restaurants and shops within walking distance as well. The tickets were less expensive as well which was ok by me! Everything about the experience from the game to the flight to the hotels to all of the amenities, the trip was perfect. Like others have said, going to a game at the Coliseum is a very special thing, so I'm sure most people would choose that option instead to watch a beat down of the 49ers, but I thought I should at least share my experience with you.