This question can only be answered by you but here are 2 things to consider that may help you decide. A Cyclura Iguana can be a lifelong committment since their lifespan can be up to 50 years compared to a Green Iguana which will live 15-20 years with good husbandry. The other consideration is just personal preference as to appearance. I love the prehistoric look of the Rhinos but an adult male Green Iguana can be a magnificent looking animal also.
Temperament is going to depend alot on what you are willing to put into the animal in time and attention. In my own experience I find the Rhinos to be more interactive and accepting of human attention. My Rhinos are my most tolerant educational animals and behave well around crowds of strangers. A long weekend away from home on display doesn't seem to have any adverse effect on them at all.
