We took the Coop Culture tour because of the price. I assume that we would have gotten a better experience with a more pricey tour (I always look on TripAdvisor to see which ones have the best reviews) but decided not to splurge in this case. The tour we went on was fine - not the highlight of our trip, but no complaints. But as others have said, it doesn't include a tour of the Forum/Palatine Hill, which might make a big difference to you, as these are all ruins and you need some help to understand what you are looking at. Rick Steves has free audiotours of both the Colosseum (though you won't be able to get underground/third ring if you are doing a DIY tour) and the forum. I checked out his Rome guide from the library and made copies of his Palatine Hill walking tour to follow along with, and bought a copy of "Rome: Past and Present" to see then and now pictures. Overall, I'd say that if cost is your priority, doing the cheaper CoopCulture tour along with Rick's free materials for the Forum/Palatine hill was just fine, but if you are looking for the complete/memorable experience, you would probably be better off finding a highly-rated tour group on TripAdvisor.