I can't tell you about either of those specific tours, but when we went a couple of years ago we rented a car in advance and did similar things on our own. My husband drove Golden Circle on the first day and we saw some volcanos the second day. I preferred Day 1 with the Geysers and Waterfalls, but mostly because the Volcano craters were more spread out so there was less to see. Research both of them online and see which one is of more interest to you. Iceland is amazing! You'll have a wonderful time.