We did both the Great Ocean Road and Phillip Island tours. Our guides were great, especially Ian on the GOR. The vehicle is comfortable and pleasant to ride in. The smaller size really did make the trip different. It was nice to talk to the other people and spend the day in a more cozy environment rather than a bigger bus. We took a tour with 18 people in Sydney and even that smaller increase makes a difference.
The sites you see on these tours are simply unbelievable. We were most impressed with the wildlife reserve on the Phillip Island tour (which compensated for the fact that there were so few penguins to be seen that night - but that's indicative of the time of year, nothing to do with the tour company). The interaction with the kangaroos was amazing. We had gone to the Featherdale Wildlife Park in the Blue Mountains, which claims interactions with kangaroos, but there is no comparison. Seeing those babies in the kangaroo pouches created memories we will never forget. The meals included in the trip are excellent, far better quality then we expected from a tour. All in all, this is an excellent tour company and you should look no further while planning these wonderful trips.
FYI, I don't think it's worth the money to pay for upgraded tours at Phillips Island. At least for the night we were there, there was not much added value for the people that did upgrade.